7ac6194c22
## Summary
Pressing Enter with an empty composer was treated as a submission, which
queued a blank message while a task was running. This PR suppresses
submission when there is no text and no attachments.
## Root Cause
- ChatComposer returned Submitted even when the trimmed text was empty.
ChatWidget then queued it during a running task, leading to an empty
item appearing in the queued list and being popped later with no effect.
## Changes
- ChatComposer Enter handling: if trimmed text is empty and there are no
attached images, return None instead of Submitted.
- No changes to ChatWidget; behavior naturally stops queuing blanks at
the source.
## Code Paths
- Modified: `tui/src/bottom_pane/chat_composer.rs`
- Tests added:
- `tui/src/bottom_pane/chat_composer.rs`: `empty_enter_returns_none`
- `tui/src/chatwidget/tests.rs`:
`empty_enter_during_task_does_not_queue`
## Result
### Before
https://github.com/user-attachments/assets/a40e2f6d-42ba-4a82-928b-8f5458f5884d
### After
https://github.com/user-attachments/assets/958900b7-a566-44fc-b16c-b80380739c92