feat: add Tauri state persistence and BvCli trait

- Add Tauri storage adapter for Zustand (tauri-storage.ts)
- Add read_state, write_state, clear_state Tauri commands
- Wire focus-store and nav-store to use Tauri persistence
- Add BvCli trait for bv CLI mocking with response types
- Add BvError and McError conversion for bv errors
- Add cleanup_tmp_files tests for bridge
- Fix linter-introduced tauri_specta::command issues

Closes bd-2x6, bd-gil, bd-3px

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

tests/stores/tauri-storage.test.ts

@@ -0,0 +1,119 @@
+/**
+ * Tests for Tauri storage adapter for Zustand.
+ *
+ * Verifies that the store persists state to Tauri backend
+ * instead of browser localStorage.
+ */
+
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+// Mock Tauri's invoke
+const mockInvoke = vi.fn();
+vi.mock("@tauri-apps/api/core", () => ({
+  invoke: (...args: unknown[]) => mockInvoke(...args),
+}));
+
+// Import after mocking
+import { createTauriStorage, initializeStorage } from "@/lib/tauri-storage";
+
+describe("Tauri Storage Adapter", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  describe("getItem", () => {
+    it("calls read_state Tauri command", async () => {
+      const savedState = { focusId: "br-123", queueOrder: ["a", "b"] };
+      mockInvoke.mockResolvedValue(savedState);
+
+      const storage = createTauriStorage();
+      const result = await storage.getItem("mc-state");
+
+      expect(mockInvoke).toHaveBeenCalledWith("read_state");
+      expect(result).toBe(JSON.stringify(savedState));
+    });
+
+    it("returns null when no state exists", async () => {
+      mockInvoke.mockResolvedValue(null);
+
+      const storage = createTauriStorage();
+      const result = await storage.getItem("mc-state");
+
+      expect(result).toBeNull();
+    });
+
+    it("returns null on Tauri error (graceful fallback)", async () => {
+      mockInvoke.mockRejectedValue(new Error("Tauri not available"));
+
+      const storage = createTauriStorage();
+      const result = await storage.getItem("mc-state");
+
+      expect(result).toBeNull();
+    });
+  });
+
+  describe("setItem", () => {
+    it("calls write_state Tauri command with parsed JSON", async () => {
+      mockInvoke.mockResolvedValue(undefined);
+
+      const storage = createTauriStorage();
+      const state = { focusId: "br-456", activeView: "queue" };
+      await storage.setItem("mc-state", JSON.stringify(state));
+
+      expect(mockInvoke).toHaveBeenCalledWith("write_state", { state });
+    });
+
+    it("handles Tauri error gracefully (does not throw)", async () => {
+      mockInvoke.mockRejectedValue(new Error("Write failed"));
+
+      const storage = createTauriStorage();
+
+      // Should not throw
+      await expect(
+        storage.setItem("mc-state", JSON.stringify({ focusId: null }))
+      ).resolves.not.toThrow();
+    });
+  });
+
+  describe("removeItem", () => {
+    it("calls clear_state Tauri command", async () => {
+      mockInvoke.mockResolvedValue(undefined);
+
+      const storage = createTauriStorage();
+      await storage.removeItem("mc-state");
+
+      expect(mockInvoke).toHaveBeenCalledWith("clear_state");
+    });
+  });
+});
+
+describe("initializeStorage", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("returns Tauri storage when in Tauri context", async () => {
+    // Tauri context detection: window.__TAURI__ exists
+    vi.stubGlobal("__TAURI__", {});
+
+    const storage = await initializeStorage();
+
+    // Should be our custom storage, not localStorage
+    expect(storage.getItem).toBeDefined();
+    expect(storage.setItem).toBeDefined();
+
+    vi.unstubAllGlobals();
+  });
+
+  it("falls back to localStorage in browser context", async () => {
+    // Not in Tauri
+    vi.stubGlobal("__TAURI__", undefined);
+
+    const storage = await initializeStorage();
+
+    // Should fall back to localStorage wrapper
+    expect(storage).toBeDefined();
+
+    vi.unstubAllGlobals();
+  });
+});