fix(matchmaking): reset phase synchronously to stop stale-ready fast-join

Leaving a match left mm.phase stuck on "ready". On the next league tap,
playLeague navigated to the matchmaking screen before svc.startMatchmaking
(which awaits connect+profile) could emit "searching" — so the screen mounted
with the old "ready" phase and its auto-enter effect instantly dropped the
player into a stale game with no lobby. Reset matchmaking to a fresh "searching"
state synchronously in the store before the async work to close the race.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/online-store.ts

@@ -148,6 +148,14 @@ export const useOnlineStore = create<OnlineStore>((set, get) => ({
   startMatchmaking: async (opts) => {
     const svc = getService();
     if (mmUnsub) mmUnsub();
+    // Reset to a fresh "searching" state SYNCHRONOUSLY before any async work. The
+    // matchmaking screen auto-enters the game when phase === "ready"; if a prior
+    // match left phase stuck on "ready", the screen would mount and fast-join a
+    // stale game before svc.startMatchmaking() (which awaits connect+profile) can
+    // emit "searching". Resetting here closes that race.
+    set({
+      matchmaking: { phase: "searching", players: [], elapsedMs: 0, ranked: opts.ranked, stake: opts.stake },
+    });
     mmUnsub = svc.onMatchmaking((s) => set({ matchmaking: s }));
     await svc.startMatchmaking(opts);
   },