fix: handle alternative JSON keys in Claude response (decklist/deck -> cards)

backend/app/services/ai/claude_client.py

@@ -60,8 +60,9 @@ def _extract_text(message) -> str:
 def _parse_json(text: str) -> dict:
     text = re.sub(r"^```(?:json)?\s*", "", text, flags=re.MULTILINE)
     text = re.sub(r"\s*```$", "", text, flags=re.MULTILINE)
+    text = text.strip()
     try:
-        return json.loads(text.strip())
+        return json.loads(text)
     except json.JSONDecodeError as e:
         raise ValueError(f"Claude response was not valid JSON: {e}\n\nRaw: {text[:500]}")
 
@@ -114,7 +115,16 @@ def _build_payload(data: dict) -> DeckPayload:
     payload = DeckPayload()
     payload.deck_name = data.get("deck_name", "Untitled Deck")
     payload.strategy_summary = data.get("strategy_summary", "")
-    for raw_card in data.get("cards", []):
+
+    # Handle both 'cards' and alternative keys Claude sometimes returns
+    cards_list = (
+        data.get("cards")
+        or data.get("decklist")
+        or data.get("deck")
+        or []
+    )
+
+    for raw_card in cards_list:
         if raw_card.get("name"):
             payload.cards.append(CardEntry(raw_card))
     for raw_cut in data.get("cuts", []):