Bug fix: ignore Enter on empty input to avoid queuing blank messages

[warpdev]

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

2025-09-02.6.11.56.mov

After

2025-09-02.6.11.31.mov