feat: enhance cleanLlmJson function to improve JSON extraction and formatting

src/llm.ts

@@ -177,9 +177,24 @@ function cleanLlmJson(text: string): string {
   const fenceMatch = text.match(/```(?:json)?\s*\n?([\s\S]*?)```/);
   let cleaned = fenceMatch ? fenceMatch[1]!.trim() : text.trim();
 
+  // Strip any non-JSON wrapper text by taking the largest JSON-looking segment
+  const firstArray = cleaned.indexOf("[");
+  const firstObject = cleaned.indexOf("{");
+  const startCandidates = [firstArray, firstObject].filter((i) => i >= 0);
+  const start = startCandidates.length > 0 ? Math.min(...startCandidates) : -1;
+  const endArray = cleaned.lastIndexOf("]");
+  const endObject = cleaned.lastIndexOf("}");
+  const end = Math.max(endArray, endObject);
+  if (start >= 0 && end > start) {
+    cleaned = cleaned.slice(start, end + 1);
+  }
+
   // Fix trailing comma-quote before closing brace: ,"} → "}
   cleaned = cleaned.replace(/,"\s*}/g, '"}');
 
+  // Fix malformed comma-quote before a closing bracket/brace: ,"} or ,"]
+  cleaned = cleaned.replace(/,\s*"\s*([}\]])/g, "$1");
+
   // Fix trailing commas before ] or }
   cleaned = cleaned.replace(/,\s*([}\]])/g, "$1");