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).

docs/src/SUMMARY.md

@@ -19,6 +19,7 @@
 - [Running the Client](getting-started/running-the-client.md)
 - [Certificate Lifecycle and CA-Signed TLS](getting-started/certificate-lifecycle.md)
 - [Docker Deployment](getting-started/docker.md)
+- [Bot SDK](getting-started/bot-sdk.md)
 - [Demo Walkthrough: Alice and Bob](getting-started/demo-walkthrough.md)
 
 ---
@@ -82,6 +83,7 @@
 - [Delivery Service Internals](internals/delivery-service.md)
 - [Authentication Service Internals](internals/authentication-service.md)
 - [Storage Backend](internals/storage-backend.md)
+- [Server Hooks (Plugin System)](internals/server-hooks.md)
 
 ---