feat(layout): finalize p01 and p02 changes

Complete UI foundation and app layout implementation, stabilize container health checks, and archive both OpenSpec changes after verification.

frontend/tests/unit/layout.store.test.ts

@@ -0,0 +1,55 @@
+import { beforeEach, describe, expect, it, vi, type Mock } from 'vitest';
+
+function getStoreValue<T>(store: { subscribe: (run: (value: T) => void) => () => void }): T {
+  let value!: T;
+  const unsubscribe = store.subscribe((current) => {
+    value = current;
+  });
+  unsubscribe();
+  return value;
+}
+
+describe('layout store', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    document.documentElement.removeAttribute('data-theme');
+    (localStorage.getItem as Mock).mockReturnValue(null);
+  });
+
+  it('initializes with default values', async () => {
+    const store = await import('../../src/lib/stores/layout');
+
+    expect(getStoreValue(store.sidebarState)).toBe('expanded');
+    expect(getStoreValue(store.theme)).toBe('light');
+  });
+
+  it('toggleSidebar cycles through states', async () => {
+    const store = await import('../../src/lib/stores/layout');
+
+    store.setSidebarState('expanded');
+    store.toggleSidebar();
+    expect(getStoreValue(store.sidebarState)).toBe('collapsed');
+    expect(localStorage.setItem).toHaveBeenCalledWith('headroom_sidebar_state', 'collapsed');
+
+    store.toggleSidebar();
+    expect(getStoreValue(store.sidebarState)).toBe('hidden');
+
+    store.toggleSidebar();
+    expect(getStoreValue(store.sidebarState)).toBe('expanded');
+  });
+
+  it('theme toggle works and applies to document', async () => {
+    const store = await import('../../src/lib/stores/layout');
+
+    store.setTheme('light');
+    store.toggleTheme();
+    expect(getStoreValue(store.theme)).toBe('dark');
+    expect(document.documentElement.getAttribute('data-theme')).toBe('dark');
+    expect(localStorage.setItem).toHaveBeenCalledWith('headroom_theme', 'dark');
+
+    store.toggleTheme();
+    expect(getStoreValue(store.theme)).toBe('light');
+    expect(document.documentElement.getAttribute('data-theme')).toBe('light');
+    expect(localStorage.setItem).toHaveBeenCalledWith('headroom_theme', 'light');
+  });
+});