feat(lobby): enter the game immediately and wait for the opponent inside it

Quick auto-match no longer waits on a separate screen: Enqueue opens a real game seating the caller with an empty opponent seat (new game status 'open') and the player enters it at once. A second human searching the same variant+rule joins that open game; otherwise a background reaper seats a robot after a 90s + random 0-90s wait, pushing a new in-app opponent_joined event that fills the opponent card and re-enables resign and chat in place.

Matchmaking state is now the open games in the database (the in-memory pool, lobby.poll and lobby.cancel are gone), serialised by a per-bucket advisory lock. While a game is open the starter may move on their turn, but resign, chat and nudge are refused; the lobby and opponent card show "searching for opponent".

Schema edited in the baseline (no prod data): 'open' status, nullable game_players.account_id for the empty seat, and a games.open_deadline_at stamp; jet code regenerated.

ui/src/screens/NewGame.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import { onDestroy, onMount } from 'svelte';
+  import { onMount } from 'svelte';
   import Screen from '../components/Screen.svelte';
   import { gateway } from '../lib/gateway';
   import { app, handleError, showToast } from '../lib/app.svelte';
@@ -41,79 +41,25 @@
   let mode = $state<'auto' | 'friends'>('auto');
 
   // --- auto-match ---
-  let searching = $state(false);
-  // matched guards the teardown: once a match arrives (immediately, via the match_found push, or
-  // via the fallback poll) onDestroy must not dequeue the game we just got.
-  let matched = $state(false);
-  let poll: ReturnType<typeof setInterval> | null = null;
-
-  function stop() {
-    if (poll) {
-      clearInterval(poll);
-      poll = null;
-    }
-  }
-  // startPoll is the matchmaking fallback used only while the live stream is down: with the stream
-  // up the match_found push drives navigation. It polls lobby.poll every 2.5s.
-  function startPoll() {
-    if (poll) return;
-    poll = setInterval(async () => {
-      try {
-        const p = await gateway.lobbyPoll();
-        if (p.matched && p.game) {
-          matched = true;
-          searching = false;
-          stop();
-          navigate(`/game/${p.game.id}`);
-        }
-      } catch (e) {
-        handleError(e);
-      }
-    }, 2500);
-  }
-  // cancelSearch leaves the auto-match pool on the backend too, so a cancelled quick-match
-  // is actually dequeued — otherwise the account stays queued (blocking a re-queue) and the
-  // reaper later substitutes a robot for a game the player abandoned.
-  function cancelSearch() {
-    stop();
-    searching = false;
-    void gateway.lobbyCancel().catch(() => {});
-    navigate('/');
-  }
+  // Enqueue drops the player straight into a real game — a freshly opened one awaiting an
+  // opponent, or another player's open game they just joined — so we navigate into it at once
+  // and the player waits inside. The opponent (a human or, after the wait, a robot) takes the
+  // empty seat later via the opponent_joined push; there is no separate "searching" screen.
+  let starting = $state(false);
 
   async function find(v: Variant) {
-    searching = true;
-    matched = false;
+    if (starting) return;
+    starting = true;
     try {
       const r = await gateway.lobbyEnqueue(v, multipleWordsForRequest(v, multipleWords));
-      if (r.matched && r.game) {
-        matched = true;
-        searching = false;
-        navigate(`/game/${r.game.id}`);
-      }
+      if (r.game) navigate(`/game/${r.game.id}`);
     } catch (e) {
-      searching = false;
       handleError(e);
+    } finally {
+      starting = false;
     }
-    // No immediate match: wait for the match_found push; the effect below polls only when the
-    // stream is down.
   }
 
-  // Poll for the match only while searching and the stream is down (the push cannot reach us);
-  // stop once the stream is back or the search ends.
-  $effect(() => {
-    if (searching && !app.streamAlive) startPoll();
-    else stop();
-  });
-  // match_found is handled globally (app.svelte navigates); end the search here too so onDestroy
-  // does not cancel the match we just received.
-  $effect(() => {
-    if (app.lastEvent?.kind === 'match_found' && searching) {
-      matched = true;
-      searching = false;
-    }
-  });
-
   // --- friend game ---
   let friends = $state<AccountRef[]>([]);
   let selected = $state<string[]>([]);
@@ -161,23 +107,10 @@
     }
   }
 
-  onDestroy(() => {
-    stop();
-    // Abandoned mid-search without a match (navigated away without Cancel): dequeue so we don't
-    // linger. A received match (matched) must not be cancelled.
-    if (searching && !matched) void gateway.lobbyCancel().catch(() => {});
-  });
 </script>
 
 <Screen title={t('new.title')} back="/">
   <div class="page">
-    {#if searching}
-      <div class="searching">
-        <div class="spinner"></div>
-        <p>{t('new.searching')}</p>
-        <button class="cancel" onclick={cancelSearch}>{t('common.cancel')}</button>
-      </div>
-    {:else}
       {#if !guest}
         <div class="seg modes">
           <button class="opt" class:active={mode === 'auto'} onclick={() => (mode = 'auto')}>{t('new.auto')}</button>
@@ -214,9 +147,10 @@
           </label>
         {/if}
         <p class="movelimit">{t('new.moveLimit', { n: AUTO_MATCH_HOURS })}</p>
+        <p class="searchhint">{t('new.searchHint')}</p>
         <button
           class="invite"
-          disabled={!selectedAuto || !connection.online}
+          disabled={!selectedAuto || !connection.online || starting}
           onclick={() => selectedAuto && find(selectedAuto)}
         >{t('new.start')}</button>
       {:else if friends.length === 0}
@@ -266,7 +200,6 @@
           <button class="invite" disabled={selected.length === 0 || !inviteVariant || !connection.online} onclick={sendInvite}>{t('new.invite')}</button>
         </div>
       {/if}
-    {/if}
   </div>
 </Screen>
 
@@ -460,31 +393,11 @@
   .invite:disabled {
     opacity: 0.5;
   }
-  .searching {
-    display: grid;
-    place-items: center;
-    gap: 14px;
-    padding: 48px 0;
+  .searchhint {
+    margin: 0;
+    text-align: center;
     color: var(--text-muted);
-  }
-  .spinner {
-    width: 36px;
-    height: 36px;
-    border: 3px solid var(--border);
-    border-top-color: var(--accent);
-    border-radius: 50%;
-    animation: spin 0.8s linear infinite;
-  }
-  @keyframes spin {
-    to {
-      transform: rotate(360deg);
-    }
-  }
-  .cancel {
-    padding: 8px 16px;
-    border: 1px solid var(--border);
-    background: var(--surface);
-    color: var(--text);
-    border-radius: var(--radius-sm);
+    font-size: 0.85rem;
+    line-height: 1.4;
   }
 </style>