Add main CLI entry point and full test suite

- bigbrother.py: Click CLI with start/stop/status/activate/deactivate/
  kill/config/selftest/modules commands plus Rich interactive menu.
  Module discovery scans modules/stealth/ for BaseModule subclasses.
  Supports --daemon mode with PID file and --passive-only flag.
- tests/conftest.py: Shared fixtures (tmp_dir, mock_config, mock_bus,
  mock_state, hardware_tier_override, project_root)
- tests/test_bus.py: 6 tests for EventBus pub/sub, filtering, wildcards
- tests/test_engine.py: 5 tests for Engine lifecycle, deps, tier, phase
- tests/test_crypto.py: 5 tests for AES-256-GCM, file encryption, KDF
- tests/test_resource.py: 7 tests for hardware detection, memory, disk
- tests/test_tool_manager.py: 6 tests for subprocess management
- tests/test_stealth_modules.py: 4 parametrized test classes covering
  all 12 stealth modules (import, inheritance, attributes, instantiation)

tests/test_resource.py

@@ -0,0 +1,85 @@
+"""Tests for utils.resource — Hardware detection and resource monitoring."""
+
+import os
+from unittest.mock import patch, mock_open
+
+import pytest
+
+from utils.resource import (
+    get_hardware_tier,
+    get_memory_info,
+    get_cpu_temperature,
+    get_disk_usage,
+    get_process_resources,
+    detect_hardware,
+    HardwareInfo,
+    TIER_GENERIC,
+    TIER_PI_ZERO,
+    TIER_OPI_ZERO3,
+)
+
+
+class TestResource:
+
+    def test_detect_hardware_tier(self):
+        """get_hardware_tier() returns a valid tier string."""
+        tier = get_hardware_tier()
+        assert tier in (TIER_GENERIC, TIER_PI_ZERO, TIER_OPI_ZERO3)
+
+    def test_detect_hardware_info(self):
+        """detect_hardware() returns a HardwareInfo dataclass."""
+        info = detect_hardware()
+        assert isinstance(info, HardwareInfo)
+        assert info.tier in (TIER_GENERIC, TIER_PI_ZERO, TIER_OPI_ZERO3)
+        assert info.cpu_cores >= 1
+        assert isinstance(info.architecture, str)
+        assert len(info.architecture) > 0
+
+    def test_get_memory_info(self):
+        """get_memory_info() returns a dict with MemTotal and MemAvailable."""
+        info = get_memory_info()
+        assert isinstance(info, dict)
+        # On Linux, /proc/meminfo should be available
+        if os.path.exists("/proc/meminfo"):
+            assert "MemTotal" in info
+            assert info["MemTotal"] > 0
+
+    def test_get_cpu_temperature(self):
+        """get_cpu_temperature() returns a float or None (no crash)."""
+        temp = get_cpu_temperature()
+        # May be None if no thermal zone is available (CI/container)
+        if temp is not None:
+            assert isinstance(temp, float)
+            # Sanity check: between -20 and 120 Celsius
+            assert -20 <= temp <= 120
+
+    def test_get_disk_usage(self):
+        """get_disk_usage() returns (total_gb, free_gb, used_pct) for /."""
+        total_gb, free_gb, used_pct = get_disk_usage("/")
+
+        assert isinstance(total_gb, float)
+        assert isinstance(free_gb, float)
+        assert isinstance(used_pct, float)
+
+        assert total_gb > 0
+        assert free_gb >= 0
+        assert 0 <= used_pct <= 100
+
+    def test_get_process_resources(self):
+        """get_process_resources() returns stats for the current PID."""
+        pid = os.getpid()
+        result = get_process_resources(pid)
+
+        # Should succeed for our own PID on Linux
+        if result is not None:
+            assert result.pid == pid
+            assert result.rss_mb >= 0
+            assert result.vms_mb >= 0
+            assert result.threads >= 1
+            assert isinstance(result.name, str)
+            assert isinstance(result.state, str)
+
+    def test_get_process_resources_invalid_pid(self):
+        """get_process_resources() returns None for a non-existent PID."""
+        result = get_process_resources(999999999)
+        assert result is None