Sidebar improvements (roadmap #10)

- sidebarCollapsed now persisted to localStorage — remembered across sessions
- Explicit ‹/› toggle button always visible in the header; no longer
  requires knowing to click the WRYSTR wordmark
  - Expanded: WRYSTR on left, ‹ collapse button on right
  - Collapsed: centered › expand button fills the header
- Write article (✦) now visible in collapsed mode as icon-only with
  tooltip, consistent with the rest of the nav
- Nav items have title tooltip in collapsed mode for discoverability
- Status footer: collapsed shows just the connection dot with tooltip;
  expanded shows dot + online/offline text + note count as before

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/stores/ui.ts

@@ -19,9 +19,11 @@ interface UIState {
   toggleSidebar: () => void;
 }
 
+const SIDEBAR_KEY = "wrystr_sidebar_collapsed";
+
 export const useUIStore = create<UIState>((set, _get) => ({
   currentView: "feed",
-  sidebarCollapsed: false,
+  sidebarCollapsed: localStorage.getItem(SIDEBAR_KEY) === "true",
   selectedPubkey: null,
   selectedNote: null,
   previousView: "feed",
@@ -34,5 +36,9 @@ export const useUIStore = create<UIState>((set, _get) => ({
     currentView: s.previousView !== s.currentView ? s.previousView : "feed",
     selectedNote: null,
   })),
-  toggleSidebar: () => set((s) => ({ sidebarCollapsed: !s.sidebarCollapsed })),
+  toggleSidebar: () => set((s) => {
+    const next = !s.sidebarCollapsed;
+    localStorage.setItem(SIDEBAR_KEY, String(next));
+    return { sidebarCollapsed: next };
+  }),
 }));