feat(ext/sw): GitHost.lastCommit() for vault-presence metadata

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

extension/src/service-worker/__tests__/git-host-extensions.test.ts

@@ -0,0 +1,55 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { GiteaHost } from '../gitea';
+import { GitHubHost } from '../github';
+
+describe('lastCommit (Gitea)', () => {
+  let fetchSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    fetchSpy = vi.spyOn(globalThis, 'fetch');
+  });
+
+  it('returns commit metadata when API succeeds', async () => {
+    fetchSpy.mockResolvedValueOnce(new Response(JSON.stringify([
+      { sha: 'abc1234567', commit: { author: { name: 'Alice', date: '2026-04-20T12:00:00Z' } } },
+    ]), { status: 200 }));
+    const host = new GiteaHost('https://git.example.com', 'user/vault', 'tok');
+    const result = await host.lastCommit('manifest.enc');
+    expect(result).toEqual({ sha: 'abc1234', author: 'Alice', date: '2026-04-20T12:00:00Z' });
+  });
+
+  it('returns null on 404', async () => {
+    fetchSpy.mockResolvedValueOnce(new Response('', { status: 404 }));
+    const host = new GiteaHost('https://git.example.com', 'user/vault', 'tok');
+    expect(await host.lastCommit('manifest.enc')).toBeNull();
+  });
+
+  it('returns null on network error', async () => {
+    fetchSpy.mockRejectedValueOnce(new Error('network'));
+    const host = new GiteaHost('https://git.example.com', 'user/vault', 'tok');
+    expect(await host.lastCommit('manifest.enc')).toBeNull();
+  });
+});
+
+describe('lastCommit (GitHub)', () => {
+  let fetchSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    fetchSpy = vi.spyOn(globalThis, 'fetch');
+  });
+
+  it('returns commit metadata when API succeeds', async () => {
+    fetchSpy.mockResolvedValueOnce(new Response(JSON.stringify([
+      { sha: 'def4567890', commit: { author: { name: 'Bob', date: '2026-04-22T15:00:00Z' } } },
+    ]), { status: 200 }));
+    const host = new GitHubHost('user/vault', 'tok');
+    const result = await host.lastCommit('manifest.enc');
+    expect(result).toEqual({ sha: 'def4567', author: 'Bob', date: '2026-04-22T15:00:00Z' });
+  });
+
+  it('returns null when commits list is empty', async () => {
+    fetchSpy.mockResolvedValueOnce(new Response(JSON.stringify([]), { status: 200 }));
+    const host = new GitHubHost('user/vault', 'tok');
+    expect(await host.lastCommit('manifest.enc')).toBeNull();
+  });
+});