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>

Cargo.lock

@@ -2880,6 +2880,7 @@ dependencies = [
  "base64 0.22.1",
  "bincode",
  "capnp",
+ "capnp-rpc",
  "capnpc",
  "chrono",
  "clap",
@@ -2904,16 +2905,24 @@ dependencies = [
  "regex",
  "reqwest",
  "rkyv",
+ "rustls",
  "serde",
  "serde_json",
  "skillratings",
  "tiktoken-rs",
  "tokio",
+ "tokio-rustls",
+ "tokio-util",
+ "toml",
+ "tracing",
+ "tracing-appender",
+ "tracing-subscriber",
  "tui-markdown",
  "tui-textarea-2",
  "unicode-width",
  "uuid",
  "walkdir",
+ "webpki-roots",
 ]
 
 [[package]]