Draft auto-save with visual indicator #113
Description
Writers lose work if the editor doesn't reliably auto-save drafts. Implement auto-save on a short interval with a visible status indicator (e.g. 'Saved', 'Saving...') in the editor toolbar.
Context: Part of the TechDiary comeback strategy — writer retention depends on trust in the editor.
Acceptance criteria:
- Auto-save triggers every 30s or on pause after typing
- Visual indicator shows last saved time or saving state
- Draft is recoverable after accidental tab close