refactor(settings): always-docked editor toolbar; reorder Navigation

The 'Always show editor toolbar' preference is gone — the docked
toolbar under the file tabs is now the only mode, and the floating
hover toolbar branch in the files editor (with its open-state and
outside-click machinery) is deleted. The stored preference is dropped
by a store migration and removed from desktop settings persistence,
settings search and every locale.

Navigation section order now reads: file editor keymap, auto-save,
terminal shell + login shell, Terminal Quick Keys, and the Session
tabs group last.

packages/ui/src/components/sections/openchamber/OpenChamberPage.tsx

@@ -154,7 +154,6 @@ const GeneralSectionContent: React.FC = () => {
                 'fileEditorKeymap',
                 ...(!isVSCode ? ['sessionTabs' as const] : []),
                 'autoSaveEnabled',
-                'expandedEditorToolbar',
                 ...(!isVSCode ? ['terminalQuickKeys' as const] : []),
                 ...(!isVSCode ? ['terminalShell' as const] : []),
                 ...(!isVSCode ? ['terminalLoginShell' as const] : []),