Edit/Preview and Save are now compact (36px) icon-only NooButtons - primary when
alone, Edit/Preview secondary beside a primary Save, a spinner circle while
saving. Plain text opens read-only like Markdown and gets the same toggle.
NooButton gains an opt-in iconOnly mode.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
A TextPreviewController (owned by the viewer, bound by MediaTextPreview)
mirrors the editing/dirty/saving state out so the top bar draws the buttons;
Save shows a spinner while saving. Located and tested via a Codex consult
(its end-to-end widget test, with the provider fixed and the saving state
adapted); the controller design replaces its builder-wrapping patch.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
