lmcp-api#83: the tray's per-AI "Disconnect" (lmcp-mac#307, lmcp-win#247; 3.0.419).

Authenticated by the machine's OWN cloud token in Authorization: Bearer <cloud_token> (never in the URL). Disconnects ONE AI (client_id, as listed by GET /oauth/connected-clients) from THIS machine: its per-AI access tokens stop working (within 30 s on every replica, at once on the one that answered) and its refresh tokens are deleted, so it must re-authorize — through the Approve dialog — to come back. Other AIs and the machine's relay are untouched.

200 {"revoked": true, "client_id", "access_tokens_revoked", "refresh_tokens_deleted"} (+ "residual_access": "none" | "machine_token" — see the return below) 400 {"error": "invalid_request"} — no client_id 401 {"error": "invalid_token"} — missing/unknown/revoked machine token 404 {"error": "not_connected"} — that AI holds nothing on this machine