lobby: a lost hub offers a reconnect

[aaylward]

After MAX_RECONNECT_ATTEMPTS (10, src/utils/hubStream.ts) the lobby shows "Lost connection to the games hub" (LobbyGame's hubLost banner) and stops. Right now the only way back is a page reload. The old /thoughts page had a reconnect button on its nav ConnectionStatus (onReconnect); that page folded into /games in #368, so its users lost it too.

Fix

• useLobby exposes reconnect(). It redials the stream (disconnect() then connect()), which is what HubWorldLink.reconnect() does today and what only useLobby.test.tsx calls. connect() clears closed, and a successful open resets reconnectAttempts, so a manual redial gets a fresh budget.
• lost clears when the redial is admitted.
• The hubLost banner gets a Reconnect button. LobbyPage passes onReconnect to its nav ConnectionStatus the same way.
• Add a Reconnect entry to the command menu (lobby/thoughts: a command palette for the world's hidden commands #349/lobby: a command menu for the world's hidden commands #370), present only while lost is set.
• Once useLobby.reconnect owns the redial, HubWorldLink.reconnect() and its redial constructor argument have no caller left; delete them.

Tests

• useLobby: exhaust the budget (fake timers), check lost is set, call reconnect(), admit the session, then check lost is cleared and the room in the permalink is rejoined.
• LobbyGame: the banner's button calls reconnect. The command-menu entry appears only while lost.
• A negative: no Reconnect button or menu entry while connected.