Previously, Space on a thinking cell hid it entirely from the transcript.
Now Space toggles between folded (summary preview) and unfolded (full
content) for thinking cells, while other cells retain the existing
hide/show behavior.
Changes:
- Add folded_thinking HashSet to App for per-cell fold tracking
- Add lines_with_options_folded / lines_with_copy_metadata_folded that
accept an explicit folded flag, overriding the global verbose setting
- Update transcript cache to pass fold state during rendering
- Update Space key handler to toggle fold for thinking cells
- Update affordance text to mention Space for expanding folded thinking
Closes#2348
Hu Qiantao
607ec155ec