test: add persistence test for nav store and update test setup

Adds test coverage for the navigation store's localStorage persistence
and ensures clean state between tests.

Changes:
- nav-store.test.ts: Add persistence test verifying activeView is saved
- Clear localStorage in beforeEach to prevent test pollution

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/stores/nav-store.test.ts

@@ -3,6 +3,7 @@ import { useNavStore } from "@/stores/nav-store";
 
 describe("useNavStore", () => {
   beforeEach(() => {
+    localStorage.clear();
     useNavStore.setState({ activeView: "focus" });
   });
 
@@ -25,4 +26,16 @@ describe("useNavStore", () => {
     useNavStore.getState().setView("focus");
     expect(useNavStore.getState().activeView).toBe("focus");
   });
+
+  describe("persistence", () => {
+    it("persists activeView to localStorage", () => {
+      useNavStore.getState().setView("queue");
+
+      const stored = localStorage.getItem("mc-nav-store");
+      expect(stored).not.toBeNull();
+
+      const parsed = JSON.parse(stored!);
+      expect(parsed.state.activeView).toBe("queue");
+    });
+  });
 });