v0.11.4 — background download daemon + tray icon

Concierge splits into a background download daemon (server) and the GUI (client), with a platform tray/menu-bar icon.

Daemon + client/server split

• concierge-daemon: a windowless background process that owns the download manager and serves it over a local socket (Unix domain socket on macOS/Linux, named pipe on Windows).
• The GUI spawn-or-connects the daemon and routes downloads to it, so a download keeps running while the window is hidden to the tray. If the daemon is unreachable, downloads run in-process exactly as before — no regression.
• The IPC protocol carries the same closed action-id vocabulary both views share; no parallel RPC surface. The daemon is the model in another process.

Tray / menu-bar icon (macOS status item, Windows notification area)

• Menu: Open Concierge / Downloads: N / Quit. Clicks flow through the one dispatch path (new show_window/quit Intents, projected + handled in the headless view, covered by the contract tests).
• Closing the window hides to the tray and keeps running; Quit from the tray is the real exit (minimize_to_tray defaults on).

Also fixed: a pre-existing startup hang where bg3::validate read modsettings.lsx (under iCloud-managed ~/Documents) synchronously — an evicted file froze launch. The read is now time-bounded.