Phase 1: project scaffold, clap CLI, self-re-exec daemon, NDJSON IPC

- Cargo.toml with clap, tokio, serde, anyhow dependencies
- Entry point with env-var routing to daemon or CLI mode
- Core protocol types (Request/Response NDJSON wire format)
- Session detection (X11 check with DISPLAY/XDG_SESSION_TYPE)
- RefMap with @wN selector resolution (direct, prefix, substring)
- Snapshot/WindowInfo shared types with Display impl
- clap derive CLI with all subcommands (snapshot, click, type, etc.)
- Client connection: socket path resolution, daemon auto-start via
  self-re-exec, NDJSON send/receive with retry backoff
- Tokio async daemon: Unix socket listener, accept loop, graceful
  shutdown via notify
- DaemonState holding session info and ref map
- Placeholder handler returning hardcoded snapshot response

src/daemon/mod.rs

@@ -0,0 +1,127 @@
+mod handler;
+mod state;
+
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use anyhow::{Context, Result};
+use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
+use tokio::net::UnixListener;
+use tokio::sync::Mutex;
+
+use crate::core::session;
+use state::DaemonState;
+
+pub fn run() -> Result<()> {
+    // Validate session before starting
+    session::detect_session()?;
+
+    let runtime = tokio::runtime::Builder::new_multi_thread()
+        .enable_all()
+        .build()?;
+
+    runtime.block_on(async_run())
+}
+
+async fn async_run() -> Result<()> {
+    let socket_path = std::env::var("DESKTOP_CTL_SOCKET_PATH")
+        .map(PathBuf::from)
+        .context("DESKTOP_CTL_SOCKET_PATH not set")?;
+
+    let pid_path = std::env::var("DESKTOP_CTL_PID_PATH")
+        .map(PathBuf::from)
+        .ok();
+
+    // Clean up stale socket
+    if socket_path.exists() {
+        std::fs::remove_file(&socket_path)?;
+    }
+
+    // Write PID file
+    if let Some(ref pid_path) = pid_path {
+        std::fs::write(pid_path, std::process::id().to_string())?;
+    }
+
+    let listener = UnixListener::bind(&socket_path)
+        .context(format!("Failed to bind socket: {}", socket_path.display()))?;
+
+    let session = std::env::var("DESKTOP_CTL_SESSION").unwrap_or_else(|_| "default".to_string());
+    let state = Arc::new(Mutex::new(DaemonState::new(session, socket_path.clone())));
+
+    let shutdown = Arc::new(tokio::sync::Notify::new());
+    let shutdown_clone = shutdown.clone();
+
+    // Accept loop
+    loop {
+        tokio::select! {
+            result = listener.accept() => {
+                match result {
+                    Ok((stream, _addr)) => {
+                        let state = state.clone();
+                        let shutdown = shutdown.clone();
+                        tokio::spawn(async move {
+                            if let Err(e) = handle_connection(stream, state, shutdown).await {
+                                eprintln!("Connection error: {e}");
+                            }
+                        });
+                    }
+                    Err(e) => {
+                        eprintln!("Accept error: {e}");
+                    }
+                }
+            }
+            _ = shutdown_clone.notified() => {
+                break;
+            }
+        }
+    }
+
+    // Cleanup
+    if socket_path.exists() {
+        let _ = std::fs::remove_file(&socket_path);
+    }
+    if let Some(ref pid_path) = pid_path {
+        let _ = std::fs::remove_file(pid_path);
+    }
+
+    Ok(())
+}
+
+async fn handle_connection(
+    stream: tokio::net::UnixStream,
+    state: Arc<Mutex<DaemonState>>,
+    shutdown: Arc<tokio::sync::Notify>,
+) -> Result<()> {
+    let (reader, mut writer) = stream.into_split();
+    let mut reader = BufReader::new(reader);
+    let mut line = String::new();
+
+    reader.read_line(&mut line).await?;
+    let line = line.trim();
+    if line.is_empty() {
+        return Ok(());
+    }
+
+    let request: crate::core::protocol::Request = serde_json::from_str(line)?;
+
+    // Handle shutdown specially - notify before writing so the accept loop
+    // exits even if the client has already closed the connection.
+    if request.action == "shutdown" {
+        shutdown.notify_one();
+        let response = crate::core::protocol::Response::ok(
+            serde_json::json!({"message": "Shutting down"})
+        );
+        let json = serde_json::to_string(&response)?;
+        // Ignore write errors - client may have already closed the connection.
+        let _ = writer.write_all(format!("{json}\n").as_bytes()).await;
+        let _ = writer.flush().await;
+        return Ok(());
+    }
+
+    let response = handler::handle_request(&request, &state).await;
+    let json = serde_json::to_string(&response)?;
+    writer.write_all(format!("{json}\n").as_bytes()).await?;
+    writer.flush().await?;
+
+    Ok(())
+}