tools: unify channel and memory tools, clean up mcp-server

Move all tool definitions and dispatch out of mcp-server.rs:
- Channel tools: new tools/channels.rs with definitions, async
  dispatch, blocking dispatch, and capnp RPC helpers
- Memory tools: make tools/memory.rs pub so mcp-server can use it

mcp-server.rs is now pure JSON-RPC protocol plumbing (482 → 169 lines).
No tool-specific code remains in that file.

Also removes duplicated channel RPC helpers and fetch_all_channels
that were in both mcp-server.rs and thalamus/channels.rs.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

Cargo.lock

@@ -623,6 +623,25 @@ dependencies = [
  "tracing-subscriber",
 ]
 
+[[package]]
+name = "consciousness-channel-tmux"
+version = "0.4.0"
+dependencies = [
+ "capnp",
+ "capnp-rpc",
+ "dirs",
+ "futures",
+ "json5",
+ "libc",
+ "poc-memory",
+ "scopeguard",
+ "serde",
+ "tokio",
+ "tokio-util",
+ "tracing",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "console-api"
 version = "0.8.1"