Content: let viewers favorite sidebar pages

[3mdistal]

Outcome

View-only collaborators can open a page sidebar overflow menu containing only Add/Remove Favorite. Favorite remains a private per-user preference; shared document mutations stay gated by edit/manage access.

Changes

• Separate personal Favorite availability from shared edit/manage capabilities in one sidebar helper.
• Apply the same gate to DatabaseSidebarRow, DocumentTreeItem, and FavoriteDocumentItem.
• Preserve existing delete, child creation, Creative Context, and drag/reorder authorization.
• Add the Content changelog entry.

Evidence

• Focused Vitest: 44 passed across role/action helper, rendered tree/Favorites menus, database-row menu, and layout tests.
• Formatting: oxfmt passed on modified source and test files.
• Patch hygiene: git diff --check passed.
• Independent technical review: approved with no findings.

The focused local run used a temporary dependency overlay from another checkout because this dedicated worktree has no node_modules; the overlay was removed. Current lockfile CI remains the authoritative test environment.

Acceptance boundary

Viewer menus expose only Add/Remove Favorite. No delete, move, child creation, drag/reorder, Creative Context, or other shared mutation is added. No feature flag, schema, action, application-state, deployment, or production setting changes are included.

Pending

CI and authenticated real-interface viewer QA. This PR is draft until those gates can be evaluated.

[github-actions]

Visual recap — skipped

The visual recap job did not run for this pull request. This is informational only and does not block the PR.

Recap skipped for d8ccf03: draft PR.