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/lib/persistence.ts

@@ -578,7 +578,6 @@ const materializeAuthoritativeUiSettings = (settings: DesktopSettings): DesktopS
     messageStreamTransport: 'auto',
     stickyUserHeader: defaults.stickyUserHeader,
     promptNavigatorEnabled: defaults.promptNavigatorEnabled,
-    expandedEditorToolbar: defaults.expandedEditorToolbar,
     wideChatLayoutEnabled: defaults.wideChatLayoutEnabled,
     showSplitAssistantMessageActions: defaults.showSplitAssistantMessageActions,
     draftStartersVisible: defaults.draftStartersVisible,
@@ -842,9 +841,6 @@ const applyDesktopUiPreferences = (settings: DesktopSettings) => {
   if (typeof settings.promptNavigatorEnabled === 'boolean' && settings.promptNavigatorEnabled !== store.promptNavigatorEnabled) {
     store.setPromptNavigatorEnabled(settings.promptNavigatorEnabled);
   }
-  if (typeof settings.expandedEditorToolbar === 'boolean' && settings.expandedEditorToolbar !== store.expandedEditorToolbar) {
-    store.setExpandedEditorToolbar(settings.expandedEditorToolbar);
-  }
   if (typeof settings.wideChatLayoutEnabled === 'boolean' && settings.wideChatLayoutEnabled !== store.wideChatLayoutEnabled) {
     store.setWideChatLayoutEnabled(settings.wideChatLayoutEnabled);
   }
@@ -1511,9 +1507,6 @@ const sanitizeWebSettings = (payload: unknown): DesktopSettings | null => {
   if (typeof candidate.promptNavigatorEnabled === 'boolean') {
     result.promptNavigatorEnabled = candidate.promptNavigatorEnabled;
   }
-  if (typeof candidate.expandedEditorToolbar === 'boolean') {
-    result.expandedEditorToolbar = candidate.expandedEditorToolbar;
-  }
   if (typeof candidate.wideChatLayoutEnabled === 'boolean') {
     result.wideChatLayoutEnabled = candidate.wideChatLayoutEnabled;
   }