Implement rotation-clone presence engine (#1) + unit tests + CI tests

- detect/PresenceEngine.kt: identity-agnostic streaming detector for key-rotating clones (novel-churn gate, seamless-handover chain, co-movement gate, coherence). Full design in docs/detection-rotation-clone.md.
- Wired into ScanService as a parallel signal; CONFIRMED verdict raises a distinct rotating-tracker alert (softer tiers stay silent pending real-capture validation).
- PresenceEngineTest: synthetic clone (moving -> CONFIRMED), stationary clone (gated), single real tracker + far-ambient (CLEAR).
- CI now runs :app:testDebugUnitTest so the engine has behavioural verification, not just a compile check.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0187UiEtasyowhEBYs6s9iF5

app/src/main/kotlin/org/soulstone/vigil/detect/PresenceEngine.kt

@@ -0,0 +1,157 @@
+package org.soulstone.vigil.detect
+
+import org.soulstone.vigil.util.Geohash
+import kotlin.math.abs
+import kotlin.math.atan2
+import kotlin.math.cos
+import kotlin.math.roundToInt
+import kotlin.math.sin
+import kotlin.math.sqrt
+
+/**
+ * The rotation-clone detector (problem #1) — the thing AirGuard and the platform
+ * detectors structurally cannot do. It ignores device identity and instead tracks
+ * whether ONE physical radio maintains an unbroken, close-range, co-moving RF
+ * *presence* even as its advertised identity churns thousands of times faster than
+ * any DULT-compliant tracker is allowed to (24h separated rotation).
+ *
+ * Streaming and pure-ish: feed separated-state sightings in time order via
+ * [onSighting]; it returns a [Verdict]. Session-scoped — call [reset] on start.
+ * Full design + rationale: docs/detection-rotation-clone.md.
+ *
+ * Key discriminator: the **seamless novel-handover chain** — a single radio whose
+ * id changes yields handovers into *novel* ids with no RSSI discontinuity and no
+ * time gap; a crowd of many radios yields gappy, RSSI-incoherent handovers. Novel
+ * churn is a *gate*, not just a score term: without it this is not a rotating
+ * clone and the (separate) identity detector owns the case.
+ */
+class PresenceEngine {
+
+    enum class Tier { CLEAR, WATCHING, PROBABLE, CONFIRMED }
+
+    data class Verdict(
+        val score: Int,
+        val tier: Tier,
+        val seamlessNovelHandovers: Int,
+        val distinctCells: Int,
+        val netMeters: Double,
+        val novelIds: Int
+    )
+
+    companion object {
+        const val R_CLOSE = -65               // dBm; the on-body/in-bag close band
+        const val G_BREAK_MS = 20_000L        // gap that ends a presence run
+        const val G_SEAM_MS = 6_000L          // handover must be near-immediate to be "seamless"
+        const val EPS_RSSI = 8.0              // dB; one radio's step-to-step RSSI
+        const val ALPHA = 0.3                 // RSSI EWMA factor
+        const val NOVELTY_HORIZON_MS = 30 * 60_000L
+        const val D_NET_M = 500.0             // co-movement: net displacement
+        const val K_CELLS = 3                 // co-movement: distinct geohash-7 cells
+        const val T_MIN_MIN = 10.0            // dwell for full duration credit
+        const val N_HANDOVER = 12             // seamless novel handovers for full credit / gate
+        const val RHO_NOVEL_PER_MIN = 0.7     // min sustained novel-seamless rate
+    }
+
+    private val seen = HashSet<String>()
+    private val seenOrder = ArrayDeque<Pair<String, Long>>()
+    private var novelCount = 0
+
+    private var active = false
+    private var startTs = 0L
+    private var lastTs = 0L
+    private var lastId: String? = null
+    private var ewmaRssi = 0.0
+    private var ewmaAbsResid = 0.0
+    private var seamlessNovel = 0
+    private val cells = HashSet<String>()
+    private var startLat = 0.0
+    private var startLon = 0.0
+    private var haveStart = false
+    private var netMeters = 0.0
+
+    @Synchronized
+    fun reset() {
+        seen.clear(); seenOrder.clear(); novelCount = 0; endRun()
+    }
+
+    @Synchronized
+    fun onSighting(id: String, rssi: Int, ts: Long, lat: Double?, lon: Double?): Verdict {
+        // Novelty bookkeeping over the horizon.
+        while (seenOrder.isNotEmpty() && ts - seenOrder.first().second > NOVELTY_HORIZON_MS) {
+            seen.remove(seenOrder.removeFirst().first)
+        }
+        val novel = id !in seen
+        if (novel) { seen.add(id); seenOrder.addLast(id to ts); novelCount++ }
+
+        // Only the close band builds a presence run.
+        if (rssi < R_CLOSE) return verdict()
+        if (!active || ts - lastTs > G_BREAK_MS) { startRun(id, rssi, ts, lat, lon); return verdict() }
+
+        val resid = rssi - ewmaRssi
+        if (id != lastId) {
+            if (abs(resid) <= EPS_RSSI && (ts - lastTs) <= G_SEAM_MS && novel) seamlessNovel++
+        }
+        ewmaRssi = ALPHA * rssi + (1 - ALPHA) * ewmaRssi
+        ewmaAbsResid = ALPHA * abs(resid) + (1 - ALPHA) * ewmaAbsResid
+        lastTs = ts; lastId = id
+        if (lat != null && lon != null) {
+            cells.add(Geohash.encode(lat, lon, 7))
+            if (haveStart) netMeters = haversineMeters(startLat, startLon, lat, lon)
+        }
+        return verdict()
+    }
+
+    private fun startRun(id: String, rssi: Int, ts: Long, lat: Double?, lon: Double?) {
+        active = true; startTs = ts; lastTs = ts; lastId = id
+        ewmaRssi = rssi.toDouble(); ewmaAbsResid = 0.0; seamlessNovel = 0
+        cells.clear(); netMeters = 0.0
+        if (lat != null && lon != null) {
+            startLat = lat; startLon = lon; haveStart = true; cells.add(Geohash.encode(lat, lon, 7))
+        } else haveStart = false
+    }
+
+    private fun endRun() {
+        active = false; lastId = null; seamlessNovel = 0; cells.clear(); netMeters = 0.0; haveStart = false
+    }
+
+    private fun verdict(): Verdict {
+        if (!active) return Verdict(0, Tier.CLEAR, 0, 0, 0.0, novelCount)
+        val durMin = (lastTs - startTs) / 60_000.0
+
+        // Novel-churn is a GATE: no impossible rotation rate => not a clone, the
+        // identity detector owns it.
+        val churnAnom = durMin > 0 && seamlessNovel >= N_HANDOVER &&
+            (seamlessNovel / durMin) >= RHO_NOVEL_PER_MIN
+        if (!churnAnom) return Verdict(0, Tier.CLEAR, seamlessNovel, cells.size, netMeters, novelCount)
+
+        val comoves = netMeters >= D_NET_M && cells.size >= K_CELLS
+        if (!comoves) {
+            // Impossible churn but co-movement not yet established (e.g. dense area) — soft only.
+            return Verdict(50, Tier.WATCHING, seamlessNovel, cells.size, netMeters, novelCount)
+        }
+
+        val coherent = ewmaAbsResid <= EPS_RSSI
+        var score = 0.0
+        score += (durMin / T_MIN_MIN).coerceIn(0.0, 1.0) * 30
+        score += (seamlessNovel.toDouble() / N_HANDOVER).coerceIn(0.0, 1.0) * 30
+        score += (cells.size.toDouble() / (2.0 * K_CELLS)).coerceIn(0.0, 1.0) * 20
+        score += (if (coherent) 1.0 else 0.4) * 20
+        val s = score.roundToInt()
+        val tier = when {
+            s >= 85 -> Tier.CONFIRMED
+            s >= 70 -> Tier.PROBABLE
+            s >= 40 -> Tier.WATCHING
+            else -> Tier.CLEAR
+        }
+        return Verdict(s, tier, seamlessNovel, cells.size, netMeters, novelCount)
+    }
+}
+
+private fun haversineMeters(lat1: Double, lon1: Double, lat2: Double, lon2: Double): Double {
+    val r = 6_371_000.0
+    val dLat = Math.toRadians(lat2 - lat1)
+    val dLon = Math.toRadians(lon2 - lon1)
+    val a = sin(dLat / 2) * sin(dLat / 2) +
+        cos(Math.toRadians(lat1)) * cos(Math.toRadians(lat2)) * sin(dLon / 2) * sin(dLon / 2)
+    return r * 2 * atan2(sqrt(a), sqrt(1 - a))
+}

app/src/main/kotlin/org/soulstone/vigil/service/ScanService.kt

@@ -28,6 +28,8 @@ import org.soulstone.vigil.data.db.TrackerEntity
 import org.soulstone.vigil.data.db.VigilDatabase
 import org.soulstone.vigil.data.location.LocationProvider
 import org.soulstone.vigil.data.settings.Settings
+import org.soulstone.vigil.detect.PresenceEngine
+import org.soulstone.vigil.model.SeparatedState
 import org.soulstone.vigil.model.TrackerObservation
 import org.soulstone.vigil.scan.BleTrackerScanner
 
@@ -46,6 +48,7 @@ class ScanService : LifecycleService() {
         private const val CHANNEL_ID = "vigil_watch"
         private const val NOTIFICATION_ID = 0x5161  // "VIGIL"
         private const val PRUNE_INTERVAL_MS = 6 * 3_600_000L
+        private const val CLONE_COOLDOWN_MS = 2 * 3_600_000L
 
         const val ACTION_START = "org.soulstone.vigil.action.START"
         const val ACTION_STOP = "org.soulstone.vigil.action.STOP"
@@ -71,6 +74,8 @@ class ScanService : LifecycleService() {
     private lateinit var repo: TrackerRepository
     private lateinit var location: LocationProvider
     private lateinit var scanner: BleTrackerScanner
+    private val presence = PresenceEngine()
+    private var lastCloneAlertMs = 0L
     private var pruneJob: Job? = null
 
     override fun onCreate() {
@@ -93,6 +98,7 @@ class ScanService : LifecycleService() {
 
     private fun begin() {
         if (_running.value) return
+        presence.reset()
         startInForeground()
         location.start()  // best-effort; scanning still runs without a fix (just no co-movement)
         if (!scanner.start()) {
@@ -110,8 +116,23 @@ class ScanService : LifecycleService() {
     }
 
     private fun onObservation(obs: TrackerObservation) {
+        val fix = location.location.value
+
+        // Rotation-clone presence engine (problem #1) — fed synchronously so its
+        // streaming state stays ordered. Only a CONFIRMED verdict raises a user
+        // alert; softer tiers stay silent until validated on real captures.
+        if (obs.separated == SeparatedState.SEPARATED) {
+            val v = presence.onSighting(obs.stableId, obs.rssi, obs.timestampMs, fix?.latitude, fix?.longitude)
+            if (v.tier == PresenceEngine.Tier.CONFIRMED &&
+                obs.timestampMs - lastCloneAlertMs > CLONE_COOLDOWN_MS
+            ) {
+                lastCloneAlertMs = obs.timestampMs
+                raiseCloneAlert()
+            }
+        }
+
+        // Temporal co-movement (identity path) — persisted + evaluated off-thread.
         lifecycleScope.launch {
-            val fix = location.location.value
             val result = runCatching {
                 repo.record(obs, fix?.latitude, fix?.longitude, settings.sensitivity.value)
             }.getOrNull() ?: return@launch
@@ -163,6 +184,17 @@ class ScanService : LifecycleService() {
         Log.w(TAG, "ALERT: ${tracker.stableId} (${tracker.ecosystem})")
     }
 
+    private fun raiseCloneAlert() {
+        val n = buildNotification(
+            title = "Possible hidden tracker",
+            text = "A rotating-ID tracker appears to be moving with you",
+            high = true
+        )
+        getSystemService(NotificationManager::class.java)?.notify(NOTIFICATION_ID + 1, n)
+        vibrate()
+        Log.w(TAG, "CLONE ALERT: rotating-id presence confirmed")
+    }
+
     private fun vibrate() {
         val v = currentVibrator() ?: return
         val effect = VibrationEffect.createWaveform(longArrayOf(0, 250, 120, 250, 120, 400), -1)

app/src/test/kotlin/org/soulstone/vigil/detect/PresenceEngineTest.kt

@@ -0,0 +1,82 @@
+package org.soulstone.vigil.detect
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * Behavioural tests for the rotation-clone [PresenceEngine], driven by synthetic
+ * traces standing in for the record/replay harness (design doc §5). Trackers
+ * advertise every ~2 s; a rotating clone changes its advertised id every 30 s.
+ */
+class PresenceEngineTest {
+
+    private val stepMs = 2_000L
+    private val steps = 900               // 30 min at 2 s
+    private val cloneRotationMs = 30_000L // Find You default
+
+    private fun maxTier(
+        idAt: (Int) -> String,
+        rssiAt: (Int) -> Int,
+        latAt: (Int) -> Double?,
+        lonAt: (Int) -> Double?
+    ): PresenceEngine.Tier {
+        val engine = PresenceEngine()
+        engine.reset()
+        var max = PresenceEngine.Tier.CLEAR
+        for (i in 0 until steps) {
+            val v = engine.onSighting(idAt(i), rssiAt(i), i * stepMs, latAt(i), lonAt(i))
+            if (v.tier.ordinal > max.ordinal) max = v.tier
+        }
+        return max
+    }
+
+    // A rotating clone that moves with the victim must be CONFIRMED.
+    @Test
+    fun cloneMovingIsConfirmed() {
+        val tier = maxTier(
+            idAt = { i -> "clone-${(i * stepMs) / cloneRotationMs}" },   // new id every 30 s
+            rssiAt = { i -> -55 + (i % 3 - 1) },                          // close, coherent
+            latAt = { 40.0 },
+            lonAt = { i -> -74.0 + i * 0.00003 }                         // marches ~2.4 km
+        )
+        assertEquals(PresenceEngine.Tier.CONFIRMED, tier)
+    }
+
+    // Same rotating churn but stationary: co-movement gate must hold it below CONFIRMED.
+    @Test
+    fun cloneStationaryIsNotConfirmed() {
+        val tier = maxTier(
+            idAt = { i -> "clone-${(i * stepMs) / cloneRotationMs}" },
+            rssiAt = { i -> -55 + (i % 3 - 1) },
+            latAt = { 40.0 },
+            lonAt = { -74.0 }                                            // fixed => no co-movement
+        )
+        assertTrue("stationary clone should not confirm, was $tier", tier.ordinal < PresenceEngine.Tier.CONFIRMED.ordinal)
+    }
+
+    // A single non-rotating tracker moving with you is NOT the presence engine's job
+    // (the identity detector owns it); the churn gate must keep this CLEAR.
+    @Test
+    fun singleRealTrackerIsClear() {
+        val tier = maxTier(
+            idAt = { "realtag" },                                        // one id, never rotates
+            rssiAt = { i -> -55 + (i % 3 - 1) },
+            latAt = { 40.0 },
+            lonAt = { i -> -74.0 + i * 0.00003 }
+        )
+        assertEquals(PresenceEngine.Tier.CLEAR, tier)
+    }
+
+    // Lots of novel ids but always far (out of the close band): no presence, CLEAR.
+    @Test
+    fun ambientFarIsClear() {
+        val tier = maxTier(
+            idAt = { i -> "ambient-$i" },                               // novel every time
+            rssiAt = { -85 },                                            // below the close band
+            latAt = { i -> 40.0 + i * 0.00003 },
+            lonAt = { -74.0 }
+        )
+        assertEquals(PresenceEngine.Tier.CLEAR, tier)
+    }
+}