Move thalamus subcrate into main crate

Move thalamus/ (poc-daemon) source files into src/thalamus/ as a
module of the main crate. The daemon entry point becomes a library
function thalamus::run() with a thin poc-daemon binary for backward
compatibility.

- Copy thalamus source into src/thalamus/, fix crate:: -> super::
- Copy daemon.capnp into schema/, add to build.rs
- Re-export daemon_capnp at crate root (capnp codegen requires it)
- Add thalamus dependencies (capnp-rpc, tokio-util, toml, rustls, etc.)
- Keep thalamus/ subcrate for comparison

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

src/lib.rs

@@ -50,6 +50,12 @@ pub mod cli;
 // TUI for memory-search
 pub mod tui;
 
+// Thalamus — notification routing and idle management daemon
+pub mod thalamus;
+
+// Re-export at crate root — capnp codegen emits `crate::daemon_capnp::` paths
+pub use thalamus::daemon_capnp;
+
 // Generated capnp bindings
 pub mod memory_capnp {
     include!(concat!(env!("OUT_DIR"), "/schema/memory_capnp.rs"));