When aborting a retry attempt, surface the retry-aware abort message
in the assistant output and tool results instead of a generic "Aborted".
- Set errorMessage for aborted streaming messages
- Render abort message without forcing a leading newline when no content
- Add configurable thinkingText color for thinking blocks (defaults to muted)
- Make 'Thinking...' label italic when collapsed
- Fix Ctrl+T during streaming hiding the current message
- Track streamingMessage to properly re-render on toggle
Based on #366 by @paulbettner