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/thalamus/tmux.rs

@@ -0,0 +1,54 @@
+// Tmux interaction: pane detection and prompt injection.
+
+use std::process::Command;
+use std::thread;
+use std::time::Duration;
+use tracing::info;
+
+/// Find Claude Code's tmux pane by scanning for the "claude" process.
+pub fn find_claude_pane() -> Option<String> {
+    let out = Command::new("tmux")
+        .args([
+            "list-panes",
+            "-a",
+            "-F",
+            "#{session_name}:#{window_index}.#{pane_index}\t#{pane_current_command}",
+        ])
+        .output()
+        .ok()?;
+
+    let stdout = String::from_utf8_lossy(&out.stdout);
+    for line in stdout.lines() {
+        if let Some((pane, cmd)) = line.split_once('\t') {
+            if cmd == "claude" {
+                return Some(pane.to_string());
+            }
+        }
+    }
+    None
+}
+
+/// Send a prompt to a tmux pane. Returns true on success.
+///
+/// Types the message literally then presses Enter.
+pub fn send_prompt(pane: &str, msg: &str) -> bool {
+    let preview: String = msg.chars().take(100).collect();
+    info!("SEND [{pane}]: {preview}...");
+
+    // Type the message literally (flatten newlines — they'd submit the input early)
+    let flat: String = msg.chars().map(|c| if c == '\n' { ' ' } else { c }).collect();
+    let ok = Command::new("tmux")
+        .args(["send-keys", "-t", pane, "-l", &flat])
+        .output()
+        .is_ok();
+    if !ok {
+        return false;
+    }
+    thread::sleep(Duration::from_millis(500));
+
+    // Submit
+    Command::new("tmux")
+        .args(["send-keys", "-t", pane, "Enter"])
+        .output()
+        .is_ok()
+}