fix(ai): strip markdown code block from Anthropic response before JSON parse

Claude Haiku wraps JSON in ```json ... ``` blocks, causing json.loads to fail
silently. The except clause swallowed the error, leaving ai_title empty for all
303 sessions.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/services/ai_session_summary.py

@@ -41,6 +41,10 @@ Return only valid JSON, no other text."""
 
     try:
         text = response.content[0].text.strip()
+        # Strip markdown code block if model wraps response (e.g. ```json ... ```)
+        if text.startswith("```"):
+            text = text.split("\n", 1)[1] if "\n" in text else text
+            text = text.rsplit("```", 1)[0].strip()
         data = json.loads(text)
         ai_title = str(data.get("title", ""))[:200]
         ai_result = str(data.get("result", ""))