docs: comprehensive update for sprints 1-9

Update README, ROADMAP, and mdBook to reflect all sprint deliverables:
rich messaging, file transfer, disappearing messages, Go/TypeScript SDKs,
C FFI, mesh networking (identity, store-and-forward, broadcast), and
security hardening. Add 6 new mdBook guides (REPL reference, Go SDK,
TypeScript SDK + browser demo, rich messaging, file transfer, mesh
networking). Check off 16 completed ROADMAP items across phases 3-9.

docs/src/SUMMARY.md

@@ -17,13 +17,19 @@
 - [Building from Source](getting-started/building.md)
 - [Running the Server](getting-started/running-the-server.md)
 - [Running the Client](getting-started/running-the-client.md)
+- [REPL Command Reference](getting-started/repl-reference.md)
+- [Rich Messaging](getting-started/rich-messaging.md)
+- [File Transfer](getting-started/file-transfer.md)
 - [TLS in quicproquo](getting-started/tls.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)
+- [Go SDK](getting-started/go-sdk.md)
+- [TypeScript SDK and Browser Demo](getting-started/typescript-sdk.md)
 - [C FFI Bindings](getting-started/ffi.md)
 - [WASM Integration](getting-started/wasm.md)
+- [Bot SDK](getting-started/bot-sdk.md)
 - [Code Generators (qpq-gen)](getting-started/generators.md)
+- [Mesh Networking](getting-started/mesh-networking.md)
 - [Demo Walkthrough: Alice and Bob](getting-started/demo-walkthrough.md)
 
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