Phase 5.7: Apply persisted Appearance live

[danielmrdev]

What to build

Restore Appearance as a temporary, accessible Settings flow. A writer can select Paper, Ink, or System and tune the curated writing layout while seeing changes immediately without altering Document or File state.

Acceptance criteria

• Settings opens and dismisses with existing shortcuts and focus behavior and exposes a real Appearance category.
• Theme, Writing width, Letter spacing, Font size, Body weight, and Document-title weight load from and persist through the existing validated Preferences domain.
• Paper and Ink use the approved Editorial Paper semantic tokens; System reacts live to supported operating-system appearance changes.
• Appearance changes preserve Document text, File state, logical caret intent, selection, and CodeMirror undo history.
• Only valid real weights and curated values are exposed, including the title-heavier-than-body invariant.
• Persistence failures leave the visible session choice active and provide retryable, non-destructive feedback.

Blocked by

• Phase 5.3: Restore, edit, autosave, and close one Document #39

Workspace

• Mode: parallel lane
• Branch: feat/tauri-2-replatform-43
• Worktree: /home/daniel/Projects/lettera/.worktrees/feat-tauri-2-replatform-43
• Integrates into: feat/tauri-2-replatform
• Remote policy: local only — never push
• Completion: when unblocked, create the lane from the latest integration commit; validate it, merge it locally into integration with approval, validate integration, remove the lane worktree, and delete the local lane branch

[danielmrdev]

Frozen by the approved UI stack decision gate in #49. Do not implement this direct-migration ticket while the Floem/Tauri bake-off is open. Native dependency #54 records the live gate. After the blind decision, this ticket will be reviewed and respecified only if Tauri wins; if Floem wins, it will be closed as replaced.