- Add onTab callback to CustomEditor
- Implement cycleThinkingLevel() in TuiRenderer
- Only works when model supports reasoning
- Cycles through: off → minimal → low → medium → high → off
- Update footer to show current thinking level with '(tab to cycle)' hint
- Update header instructions to mention tab for thinking
- Show notification when thinking level changes
Tino Ehrich
9e8373b86a