feat: Phase 9 — developer experience, extensibility, and community growth

New crates:
- quicproquo-bot: Bot SDK with polling API + JSON pipe mode
- quicproquo-kt: Key Transparency Merkle log (RFC 9162 subset)
- quicproquo-plugin-api: no_std C-compatible plugin vtable API
- quicproquo-gen: scaffolding tool (qpq-gen plugin/bot/rpc/hook)

Server features:
- ServerHooks trait wired into all RPC handlers (enqueue, fetch, auth,
  channel, registration) with plugin rejection support
- Dynamic plugin loader (libloading) with --plugin-dir config
- Delivery proof canary tokens (Ed25519 server signatures on enqueue)
- Key Transparency Merkle log with inclusion proofs on resolveUser

Core library:
- Safety numbers (60-digit HMAC-SHA256 key verification codes)
- Verifiable transcript archive (CBOR + ChaCha20-Poly1305 + hash chain)
- Delivery proof verification utility
- Criterion benchmarks (hybrid KEM, MLS, identity, sealed sender, padding)

Client:
- /verify REPL command for out-of-band key verification
- Full-screen TUI via Ratatui (feature-gated --features tui)
- qpq export / qpq export-verify CLI subcommands
- KT inclusion proof verification on user resolution

Also: ROADMAP Phase 9 added, bot SDK docs, server hooks docs,
crate-responsibilities updated, example plugins (rate_limit, logging).

Cargo.toml

@@ -3,8 +3,12 @@ resolver = "2"
 members = [
     "crates/quicproquo-core",
     "crates/quicproquo-proto",
+    "crates/quicproquo-plugin-api",
+    "crates/quicproquo-kt",
     "crates/quicproquo-server",
     "crates/quicproquo-client",
+    "crates/quicproquo-bot",
+    "crates/quicproquo-gen",
     "crates/quicproquo-gui",
     "crates/quicproquo-mobile",
     # P2P crate uses iroh (~90 extra deps). Kept in the workspace so it can be
@@ -29,7 +33,9 @@ ml-kem             = { version = "0.2" }
 x25519-dalek       = { version = "2", features = ["static_secrets"] }
 ed25519-dalek      = { version = "2", features = ["rand_core"] }
 sha2               = { version = "0.10" }
+hmac               = { version = "0.12" }
 hkdf               = { version = "0.12" }
+ciborium           = { version = "0.2" }
 chacha20poly1305   = { version = "0.10" }
 opaque-ke          = { version = "4", features = ["ristretto255", "argon2"] }
 zeroize            = { version = "1", features = ["derive", "serde"] }