test: add comprehensive frontend tests for components, stores, and utils

Full test coverage for the frontend implementation using Vitest and
Testing Library. Tests are organized by concern with shared fixtures.

Component tests:
- AppShell.test.tsx: Navigation tabs, view switching, batch mode overlay
- FocusCard.test.tsx: Rendering, action buttons, keyboard shortcuts, empty state
- QueueView.test.tsx: Item display, focus promotion, empty state
- QueueItem.test.tsx: Type badges, click handling
- QueueSummary.test.tsx: Count display by type
- QuickCapture.test.tsx: Modal behavior, form submission, error states
- BatchMode.test.tsx: Progress tracking, item advancement, completion
- App.test.tsx: Updated for AppShell integration

Store tests:
- focus-store.test.ts: Item management, act(), setFocus(), reorderQueue()
- nav-store.test.ts: View switching
- capture-store.test.ts: Open/close, submission states
- batch-store.test.ts: Batch lifecycle, status tracking, derived counts

Library tests:
- types.test.ts: Type guards, staleness computation
- transform.test.ts: Lore data transformation, priority ordering
- format.test.ts: IID formatting for MRs vs issues

E2E tests (app.spec.ts):
- Navigation flow
- Focus card interactions
- Queue management
- Quick capture flow

Test infrastructure:
- fixtures.ts: makeFocusItem() factory
- tauri-plugin-shell.ts: Mock for @tauri-apps/plugin-shell
- Updated tauri-api.ts mock with new commands
- vitest.config.ts: Path aliases, jsdom environment
- playwright.config.ts: Removed webServer (run separately)
- package.json: Added @tauri-apps/plugin-shell dependency

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

tests/lib/types.test.ts

@@ -0,0 +1,59 @@
+import { describe, it, expect } from "vitest";
+import { computeStaleness, isMcError } from "@/lib/types";
+
+describe("computeStaleness", () => {
+  it("returns 'normal' for null timestamp", () => {
+    expect(computeStaleness(null)).toBe("normal");
+  });
+
+  it("returns 'fresh' for items less than 1 day old", () => {
+    const twoHoursAgo = new Date(Date.now() - 2 * 60 * 60 * 1000).toISOString();
+    expect(computeStaleness(twoHoursAgo)).toBe("fresh");
+  });
+
+  it("returns 'normal' for items 1-2 days old", () => {
+    const thirtyHoursAgo = new Date(
+      Date.now() - 30 * 60 * 60 * 1000
+    ).toISOString();
+    expect(computeStaleness(thirtyHoursAgo)).toBe("normal");
+  });
+
+  it("returns 'amber' for items 3-6 days old", () => {
+    const fourDaysAgo = new Date(
+      Date.now() - 4 * 24 * 60 * 60 * 1000
+    ).toISOString();
+    expect(computeStaleness(fourDaysAgo)).toBe("amber");
+  });
+
+  it("returns 'urgent' for items 7+ days old", () => {
+    const tenDaysAgo = new Date(
+      Date.now() - 10 * 24 * 60 * 60 * 1000
+    ).toISOString();
+    expect(computeStaleness(tenDaysAgo)).toBe("urgent");
+  });
+});
+
+describe("isMcError", () => {
+  it("returns true for valid McError objects", () => {
+    const error = {
+      code: "LORE_UNAVAILABLE",
+      message: "lore CLI not found",
+      recoverable: true,
+    };
+    expect(isMcError(error)).toBe(true);
+  });
+
+  it("returns false for plain strings", () => {
+    expect(isMcError("some error")).toBe(false);
+  });
+
+  it("returns false for null", () => {
+    expect(isMcError(null)).toBe(false);
+  });
+
+  it("returns false for objects missing required fields", () => {
+    expect(isMcError({ code: "TEST" })).toBe(false);
+    expect(isMcError({ message: "test" })).toBe(false);
+    expect(isMcError({ recoverable: true })).toBe(false);
+  });
+});