feat(tcg): add burn UI to collection, build passes

- CollectionView: burn mode with 5-card selection (commons only)
- Burn bar with confirmation, reward cookies credited
- Selected cards highlighted with fire emoji
- Non-common cards dimmed in burn mode
- a11y: role/tabIndex/onKeyDown for keyboard navigation
- Vite build: EXIT_CODE=0 (max-old-space-size=3072)
- All 250 tests pass (106 backend + 46 protocol + 98 frontend)

apps/client/src/botsu/tcg/BotsuTcgPage.tsx

@@ -142,6 +142,10 @@ function CollectionView() {
   const [rarity, setRarity] = useState<TcgRarity | undefined>(undefined);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
+  const [selected, setSelected] = useState<Set<string>>(new Set());
+  const [burnMode, setBurnMode] = useState(false);
+  const [burning, setBurning] = useState(false);
+  const [burnResult, setBurnResult] = useState<{ burned: number; reward: number; balance: number } | null>(null);
 
   const load = useCallback(async () => {
     setLoading(true);
@@ -160,6 +164,38 @@ function CollectionView() {
     load().catch(() => undefined);
   }, [load]);
 
+  const toggleSelect = (instanceId: string) => {
+    setSelected((prev) => {
+      const next = new Set(prev);
+      if (next.has(instanceId)) {
+        next.delete(instanceId);
+      } else if (next.size < 5) {
+        next.add(instanceId);
+      }
+      return next;
+    });
+  };
+
+  const doBurn = async () => {
+    if (selected.size !== 5) return;
+    setBurning(true);
+    setError(null);
+    try {
+      const result = await controller.burnCards([...selected]);
+      setBurnResult({ burned: result.burned.length, reward: result.reward, balance: result.balance });
+      setSelected(new Set());
+      setBurnMode(false);
+      await load();
+    } catch (e) {
+      setError((e as Error).message);
+    } finally {
+      setBurning(false);
+    }
+  };
+
+  const selectedCount = selected.size;
+  const canBurn = selectedCount === 5;
+
   return (
     <div>
       <div className="botsu-tcg-filters">
@@ -182,7 +218,33 @@ function CollectionView() {
             {RARITY_LABELS[r]}
           </button>
         ))}
+        <button
+          type="button"
+          className="botsu-tcg-filter-btn"
+          data-active={burnMode}
+          onClick={() => { setBurnMode(!burnMode); setSelected(new Set()); }}
+        >
+          Brûler
+        </button>
       </div>
+      {burnMode && (
+        <div className="botsu-tcg-burn-bar">
+          <span>Sélectionne 5 cartes communes à brûler ({selectedCount}/5)</span>
+          <button
+            type="button"
+            className="botsu-tcg-booster-btn"
+            onClick={doBurn}
+            disabled={!canBurn || burning}
+          >
+            {burning ? '…' : 'Confirmer le brûlage'}
+          </button>
+        </div>
+      )}
+      {burnResult && (
+        <div className="botsu-tcg-burn-result">
+          {burnResult.burned} cartes brûlées. Récompense: {burnResult.reward} cookies. Solde: {burnResult.balance}
+        </div>
+      )}
       {error && <div className="botsu-tcg-error">{error}</div>}
       {loading && <div className="botsu-tcg-loading">Chargement…</div>}
       {page && !loading && (
@@ -192,7 +254,21 @@ function CollectionView() {
           ) : (
             <div className="botsu-tcg-cards">
               {page.cards.map((card) => (
-                <CardView key={card.instanceId} card={card} />
+                <div
+                  key={card.instanceId}
+                  data-selected={burnMode && selected.has(card.instanceId)}
+                  role={burnMode && card.rarity === 'common' ? 'button' : undefined}
+                  tabIndex={burnMode && card.rarity === 'common' ? 0 : undefined}
+                  onClick={burnMode && card.rarity === 'common' ? () => toggleSelect(card.instanceId) : undefined}
+                  onKeyDown={
+                    burnMode && card.rarity === 'common'
+                      ? (e) => { if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); toggleSelect(card.instanceId); } }
+                      : undefined
+                  }
+                  style={burnMode && card.rarity !== 'common' ? { opacity: 0.3, pointerEvents: 'none' } : undefined}
+                >
+                  <CardView card={card} />
+                </div>
               ))}
             </div>
           )}

apps/client/src/botsu/tcg/tcg.css

@@ -329,4 +329,50 @@
   border-radius: var(--botsu-radius);
   text-transform: uppercase;
   font-weight: 700;
+}
+
+/* Burn mode */
+.botsu-tcg-burn-bar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 1rem;
+  padding: 0.8rem 1rem;
+  background: color-mix(in srgb, #e55 10%, var(--botsu-color-surface));
+  border: 1px solid color-mix(in srgb, #e55 40%, transparent);
+  border-radius: var(--botsu-radius);
+  margin-bottom: 0.5rem;
+}
+
+.botsu-tcg-burn-bar span {
+  font-size: 0.85rem;
+  color: var(--botsu-color-text-muted);
+}
+
+.botsu-tcg-burn-bar button {
+  font-size: 0.8rem;
+  padding: 0.5rem 1.5rem;
+}
+
+.botsu-tcg-burn-result {
+  padding: 0.6rem 1rem;
+  background: color-mix(in srgb, #4a9 10%, var(--botsu-color-surface));
+  border: 1px solid color-mix(in srgb, #4a9 40%, transparent);
+  border-radius: var(--botsu-radius);
+  font-size: 0.85rem;
+  margin-bottom: 0.5rem;
+}
+
+.botsu-tcg-cards > [data-selected="true"] .botsu-tcg-card {
+  border-color: #e55;
+  box-shadow: 0 0 8px color-mix(in srgb, #e55 30%, transparent);
+}
+
+.botsu-tcg-cards > [data-selected="true"]::before {
+  content: '🔥';
+  position: absolute;
+  margin-left: -0.3rem;
+  margin-top: -0.3rem;
+  font-size: 1rem;
+  z-index: 1;
 }