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/core/mod.rs

@@ -0,0 +1,4 @@
+pub mod protocol;
+pub mod refs;
+pub mod session;
+pub mod types;