R5: consent-gated recruitment + per-hop X25519 sealed credentials

Add the in-band, signature-gated consent handshake that governs whether a
node may be recruited into a measured SOR circuit, plus a per-recipient
sealed box so a hop credential decrypts only with the host's X25519 key.

- crypto.rs: seal_to_pubkey/open_sealed (ephemeral X25519 -> HKDF-SHA256 ->
  Fernet AEAD), reusing the existing fernet crate (no new symmetric primitive).
- sor/consent.rs: signed ConsentRequest (Ed25519 persona), node_evaluate
  (reject unless the signature verifies), CircuitBuilder that recruits a hop
  only on an accept it can open; parse_sor_frame with never-panic proptests.
- net.rs: {"_sor":...} control frames are live-only and classified out-of-band
  by the SOR layer (parse_sor), never surfaced as chat/app events.
- cmd_chat/sor/consent.py + bridge _sor case: bit-compatible Python mirror;
  the agent only observes/classifies consent frames — it never auto-accepts
  and stands up no forwarder (forwarding is R4, isolated-engine-only).

Acceptance check (roadmap R5) green both languages: host recruits a hop only
after an explicit accept; a reject leaves no entry; the credential opens only
with the host key (third party cannot); unsigned/forged request -> rejected.
Cross-language KDF parity pinned by a shared known-answer vector.
Rust 75 passed; Python SOR suite 37 passed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hh/Cargo.lock

@@ -297,6 +297,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "cpufeatures"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b2a41393f66f16b0823bb79094d54ac5fbd34ab292ddafb9a0456ac9f87d201"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "crossterm"
 version = "0.28.1"
@@ -340,10 +349,25 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "97fb8b7c4503de7d6ae7b42ab72a5a59857b4c937ec27a3d4539dba95b5ab2be"
 dependencies = [
  "cfg-if",
- "cpufeatures",
+ "cpufeatures 0.2.17",
  "curve25519-dalek-derive",
  "digest",
- "fiat-crypto",
+ "fiat-crypto 0.2.9",
+ "rustc_version",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "curve25519-dalek"
+version = "5.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5eed333089e2e1c1ac8c6c0398e5e2497b4c9926ca6d0365ed1e099afa5bc23"
+dependencies = [
+ "cfg-if",
+ "cpufeatures 0.3.0",
+ "curve25519-dalek-derive",
+ "fiat-crypto 0.3.0",
  "rustc_version",
  "subtle",
  "zeroize",
@@ -460,7 +484,7 @@ version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "70e796c081cee67dc755e1a36a0a172b897fab85fc3f6bc48307991f64e4eca9"
 dependencies = [
- "curve25519-dalek",
+ "curve25519-dalek 4.1.3",
  "ed25519",
  "serde",
  "sha2",
@@ -515,6 +539,12 @@ version = "0.2.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "28dea519a9695b9977216879a3ebfddf92f1c08c05d984f8996aecd6ecdc811d"
 
+[[package]]
+name = "fiat-crypto"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "64cd1e32ddd350061ae6edb1b082d7c54915b5c672c389143b9a63403a109f24"
+
 [[package]]
 name = "filedescriptor"
 version = "0.8.3"
@@ -713,6 +743,7 @@ dependencies = [
  "tungstenite",
  "url",
  "vt100",
+ "x25519-dalek",
 ]
 
 [[package]]
@@ -1502,6 +1533,12 @@ dependencies = [
  "getrandom 0.3.4",
 ]
 
+[[package]]
+name = "rand_core"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "63b8176103e19a2643978565ca18b50549f6101881c443590420e4dc998a3c69"
+
 [[package]]
 name = "rand_xorshift"
 version = "0.4.0"
@@ -1830,7 +1867,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e3bf829a2d51ab4a5ddf1352d8470c140cadc8301b2ae1789db023f01cedd6ba"
 dependencies = [
  "cfg-if",
- "cpufeatures",
+ "cpufeatures 0.2.17",
  "digest",
 ]
 
@@ -1841,7 +1878,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a7507d819769d01a365ab707794a4084392c824f54a7a6a7862f8c3d0892b283"
 dependencies = [
  "cfg-if",
- "cpufeatures",
+ "cpufeatures 0.2.17",
  "digest",
 ]
 
@@ -2767,6 +2804,17 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1ffae5123b2d3fc086436f8834ae3ab053a283cfac8fe0a0b8eaae044768a4c4"
 
+[[package]]
+name = "x25519-dalek"
+version = "3.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e7e8131a03190127fb2263afc72b322ecadae46b6ff8c6f399ff5d02f5559af6"
+dependencies = [
+ "curve25519-dalek 5.0.0",
+ "rand_core 0.10.1",
+ "zeroize",
+]
+
 [[package]]
 name = "xattr"
 version = "1.6.1"