MCP server: distinguish answer file read errors from empty recall results #13

Context

Follow-up from review on PR #10

In examples/mcp_server.py → run_recall(), when temp_ans_file.read_text() raises an exception (e.g. file read/permission error or damaged descriptor), the except Exception: block currently catches it with pass and falls through to "(no matching notes found)", True.

While isError: True is correctly set (preventing the agent from trusting anything), an I/O read failure is masked behind a "no matching notes found" message.

Proposed Fix

1. In run_recall(), capture except Exception as e: and return an explicit error string:
   return f"Recall error: failed to read answer file: {e}", True
2. Keep "(no matching notes found)", True strictly for when the answer file was read without errors, but has empty content.
3. Add a unit test verifying read errors produce distinct error text with isError: True.