fix(editor): make Settings modal and toolbar trailer truly global

[DavidBabinec]

What changed

Two related fixes so the admin Settings modal and the toolbar settings cog behave globally on every admin route.

1. Settings General + Publishing now load on every page

GeneralSection and PublishingSection read site data straight off the heavy editor store (@site/store/store), which is only hydrated by usePersistence on the Site editor. On Content / Data / Media / Plugins / Users / Account, the editor store's site is null, so those sections rendered a permanent skeleton (see the original bug screenshots). The modal was "global" in name only.

New useSiteSettingsController (src/admin/modals/Settings/useSiteSettingsController.ts) exposes one uniform site-settings shape and picks the right source:

• Site editor (live draft in the editor store) → delegate to the editor-store mutations, so settings edits join the unsaved draft and persist through autosave / Save alongside page-tree edits.
• Everywhere else (no in-memory draft) → a standalone store loads the document via cmsAdapter, edits a local copy, and persists immediately with a shell-only saveSite (empty dirty sets → pages/components/layouts untouched), then refreshes the adminUi site summary and fires CMS_SITE_RELOAD_EVENT.

The controller is imported only by the lazy SettingsModal sections, so the editor-store import stays inside the settings chunk and never enters the eager graph of the lightweight layouts — the bundle-isolation contract holds.

2. Settings cog is now a consistent, global part of the header

The Toolbar shell already always rendered OpenLivePageButton + AccountMenuButton, but SettingsButton was injected per-layout — Site, Plugins/Users/Account, and Content had it; Media and Data did not.

SettingsButton is hoisted into Toolbar.tsx as part of a fixed global trailer (Settings → Open live page → Account), identical on every route the way the left nav is. Removed the per-layout/per-page injections (AdminCanvasLayout, AdminPageLayout, ContentToolbar) and the now-dead ToolbarDivider + .divider CSS. SettingsButton reads only the tiny adminUi store, so hosting it in the shell doesn't drag the editor toolchain into non-editor bundles.

User/developer impact

• The Settings modal's General and Publishing sections work from any admin page, not just the Site editor.
• The settings cog appears in the same place on every admin page (Media and Data gain it; no page renders a duplicate).
• Editing site settings outside the Site editor saves immediately (those pages have no Save button).

Verification

• bun run build (tsc -b && vite build) — clean
• bun test — 5442 pass, 0 fail
• bun run lint — clean on changed files

Updated toolbar.test.ts (settings cog is now asserted in the shell, not AdminCanvasLayout) and docs/editor.md (global trailer + controller).

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