fix(closet_llm): retry _call_llm on JSONDecodeError instead of bailing

The retry loop already backs off on HTTP 429/503 and rate-limit-shaped
exceptions, but JSONDecodeError exited on the first failure. Local LLM
runtimes occasionally produce malformed JSON (truncated streams, partial
chunks under load), and the retry was effectively dead for that path.

Mirror the 429/503 branch: sleep with exponential backoff and continue
through all 3 attempts, only returning None after the final failure.

Closes #1155

mempalace/closet_llm.py

@@ -169,6 +169,9 @@ def _call_llm(cfg: LLMConfig, source_file: str, wing: str, room: str, content: s
             parsed = json.loads(text)
             return parsed, payload.get("usage")
         except json.JSONDecodeError:
+            if attempt < 2:
+                time.sleep(2**attempt)
+                continue
             return None, None
         except urllib.error.HTTPError as e:
             # 429 / 503 = retry with backoff