fix: address code review feedback from coderabbitai

- Add language specifier to fenced code block in expand-project.md
- Remove detailed exception strings from WebSocket responses (security)
- Make WebSocket "start" message idempotent to avoid session reset
- Fix race condition in bulk feature creation with row-level lock
- Add validation for starting_priority (must be >= 1)
- Fix _query_claude to handle multiple feature blocks and deduplicate
- Add FileReader error handling in ExpandProjectChat
- Fix disconnect() to clear pending reconnect timeout
- Enable sandbox mode and validate CLI path in expand_chat_session
- Clean up temporary settings file on session close

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/commands/expand-project.md

@@ -144,7 +144,7 @@ Once the user approves, create features directly.
 
 **Then output the features in this exact JSON format (the system will parse this):**
 
-```
+```json
 <features_to_create>
 [
   {