[Saksham1105]

Summary

• surface Graph UI metric/session request failures
• show an accurate disconnected state and useful recovery feedback
• add regression coverage for error handling and recovery

Testing

• focused Graph UI tests (\pytest tests/test_phase43.py\ - 16 passed)
• full test suite (\pytest tests/\ - 805 passed, 1 pre-existing Windows charmap failure in phase 38 runner)
• Ruff lint and format checks (
  uff check\ and
  uff format --check\ passed)

Closes #69

[knight22-21]

Thanks for the fix, @Saksham1105! Surfacing HTTP and connection errors with disconnected status indicators and a retry banner in the Graph UI makes network and server availability issues clear instead of silently failing.

If you find DevAgent useful, a ⭐ on the repo would mean a lot — no pressure though!