feat: honest AI opponent in quick game

New Game's quick game gains an explicit opponent selector — 🤖 AI (default)
or 👤 Random player. AI starts a game seated with a pooled robot that joins
and moves at once: no per-move timeout (a 7-day inactivity loss reusing the
turn-timeout sweeper), chat/nudge disabled, no statistics, the opponent shown
as 🤖 everywhere. The random path (disguised robot) is unchanged.

Driven by one game flag (games.vs_ai), set only on AI-started games so the
disguised path is never revealed; Matchmaker.StartVsAI seats the robot
directly (no open pool); the robot replies event-driven via the game service's
after-commit/after-create hook. Wire: vs_ai on EnqueueRequest + GameView.

ui/src/game/Chat.svelte

@@ -12,6 +12,7 @@
     canNudge = false,
     waiting = false,
     nudgeOnCooldown = false,
+    vsAi = false,
     onsend,
     onnudge,
   }: {
@@ -34,6 +35,9 @@
     // are disabled (there is no one to message or hurry yet).
     waiting?: boolean;
     nudgeOnCooldown?: boolean;
+    // vsAi disables both controls in an honest-AI game: the opponent is a robot, so there is
+    // nobody to message or hurry. The fields still show (turn-driven), but disabled.
+    vsAi?: boolean;
     onsend: (text: string) => void;
     onnudge: () => void;
   } = $props();
@@ -67,9 +71,10 @@
         maxlength="60"
         placeholder={t('chat.placeholder')}
         bind:value={text}
-        onkeydown={(e) => e.key === 'Enter' && !busy && send()}
+        disabled={vsAi}
+        onkeydown={(e) => e.key === 'Enter' && !busy && !vsAi && send()}
       />
-      <button class="iconbtn" onclick={send} disabled={busy || waiting || !connection.online} aria-label={t('chat.send')}>⬆️</button>
+      <button class="iconbtn" onclick={send} disabled={busy || waiting || vsAi || !connection.online} aria-label={t('chat.send')}>⬆️</button>
     {:else if myTurn}
       <!-- Own turn, the one allowed message already sent: a caption holds the row until the
            next turn (no nudge — there is no one to hurry on your own turn). -->
@@ -77,7 +82,7 @@
     {:else if canNudge}
       <!-- A flex:1 caption keeps the nudge pinned right whether or not the cooldown text shows. -->
       <span class="cooldown">{nudgeOnCooldown ? t('chat.awaitingReply') : ''}</span>
-      <button class="iconbtn" onclick={onnudge} disabled={busy || waiting || nudgeOnCooldown || !connection.online} aria-label={t('chat.nudgeAction')}>🛎️</button>
+      <button class="iconbtn" onclick={onnudge} disabled={busy || waiting || nudgeOnCooldown || vsAi || !connection.online} aria-label={t('chat.nudgeAction')}>🛎️</button>
     {/if}
   </div>
 </div>