Stage 17 round 5 — backend/correctness bug fixes

- Resign on the opponent's turn: engine ResignSeat(seat) resigns a specific seat
  (not just toMove); game.Resign bypasses the turn check and forfeits the actor's seat.
- Quick-match cancel was a UI no-op (only stopped polling): add the full path
  (REST /lobby/cancel -> gateway lobby.cancel -> client) and clear the matchmaker's
  pending result on Cancel, so a cancelled search is dequeued (no 'already queued', no
  later robot-substituted game). NewGame dequeues on cancel and on abandon.
- Lobby win/loss: result.ts ranked by score, so a 0-0 resignation read as a win.
  The winner now takes rank 1 and the viewer is placed from rank 2 — matching the
  game-detail screen.
- Friend request to a robot: robots no longer block requests; the request stays
  pending and expires (friendRequestTTL), mirroring a human who ignores it.
- Nudge cooldown: ErrNudgeTooSoon now maps to a distinct nudge_too_soon code with a
  correct message; the chat nudge button disables during the hourly cooldown; the
  nudge note reads 'Waiting for your move!' (button keeps the Nudge action label).
Tests: engine/service off-turn resign, matchmaker cancel-clears-result, friend-to-robot
inttest, result.ts 0-0 resignation, nudge_too_soon mapping.

ui/src/screens/NewGame.svelte

@@ -31,12 +31,22 @@
       poll = null;
     }
   }
+  // 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 (Stage 17 fix).
+  function cancelSearch() {
+    stop();
+    searching = false;
+    void gateway.lobbyCancel().catch(() => {});
+    navigate('/');
+  }
 
   async function find(v: Variant) {
     searching = true;
     try {
       const r = await gateway.lobbyEnqueue(v);
       if (r.matched && r.game) {
+        searching = false;
         navigate(`/game/${r.game.id}`);
         return;
       }
@@ -45,6 +55,7 @@
           const p = await gateway.lobbyPoll();
           if (p.matched && p.game) {
             stop();
+            searching = false;
             navigate(`/game/${p.game.id}`);
           }
         } catch (e) {
@@ -103,7 +114,11 @@
     }
   }
 
-  onDestroy(stop);
+  onDestroy(() => {
+    stop();
+    // Abandoned mid-search (navigated away without Cancel): dequeue so we don't linger.
+    if (searching) void gateway.lobbyCancel().catch(() => {});
+  });
 </script>
 
 <Screen title={t('new.title')} back="/">
@@ -112,7 +127,7 @@
       <div class="searching">
         <div class="spinner"></div>
         <p>{t('new.searching')}</p>
-        <button class="cancel" onclick={() => { stop(); navigate('/'); }}>{t('common.cancel')}</button>
+        <button class="cancel" onclick={cancelSearch}>{t('common.cancel')}</button>
       </div>
     {:else}
       {#if !guest}