refactor(maestro): flatten web UI to a single host

Session tree nests by working directory only; the daemon chips in the
header become a session tally, and the spawn form loses its host picker.
API calls move from /api/daemons/:id/* to /api/dirs, /api/recent-dirs,
/api/gitroot, and /api/info.

web/src/hud.ts

@@ -15,7 +15,6 @@ import { sessionName, type Session, type Uuid } from "./types.js";
  * them. Everything else on the Session is shown, including future fields. */
 const CLIENT_OWNED = new Set([
   "id",
-  "daemon_id",
   "cwd",
   "command",
   "env",