feat: add E2E testing infrastructure with real Chrome in CI

## Changes

### E2E Test Suite (~52 test cases)
- public-commands.test.ts — Public API commands (hackernews, v2ex)
- browser-public.test.ts — Browser commands for public data across all sites
- browser-auth.test.ts — Graceful failure verification for login-required commands
- management.test.ts — Full coverage of management commands
- output-formats.test.ts — Output format validation (json/yaml/csv/md)
- smoke/api-health.test.ts — Scheduled API health checks

### Auto-detect Browser Mode
- buildMcpArgs uses CI env var to select mode:
  - Local (no CI) → --extension (connect to user's Chrome)
  - CI → standalone (launches its own browser)

### CI Pipeline
- e2e-headed.yml — Real Chrome via setup-chrome + xvfb in headed mode
- ci.yml — build + unit-test (2 shards) + smoke-test (scheduled/manual)
- Composite action for shared Chrome + xvfb setup

### Documentation
- New TESTING.md — Architecture, coverage, local setup, how to add tests

Co-authored-by: AlexYue <yj976240184@qq.com>

.github/actions/setup-chrome/action.yml

@@ -0,0 +1,26 @@
+name: Setup Chrome + xvfb
+description: Install real Chrome and xvfb virtual display for headed browser testing
+
+outputs:
+  chrome-path:
+    description: Path to the installed Chrome binary
+    value: ${{ steps.setup-chrome.outputs.chrome-path }}
+
+runs:
+  using: composite
+  steps:
+    - name: Install real Chrome (stable)
+      uses: browser-actions/setup-chrome@v1
+      id: setup-chrome
+      with:
+        chrome-version: stable
+
+    - name: Verify Chrome installation
+      shell: bash
+      run: |
+        echo "Chrome path: ${{ steps.setup-chrome.outputs.chrome-path }}"
+        ${{ steps.setup-chrome.outputs.chrome-path }} --version
+
+    - name: Install xvfb for headed mode
+      shell: bash
+      run: sudo apt-get install -y xvfb

.github/workflows/ci.yml

@@ -2,12 +2,16 @@ name: CI
 
 on:
   push:
-    branches: [main]
+    branches: [main, dev]
   pull_request:
-    branches: [main]
+    branches: [main, dev]
+  schedule:
+    - cron: '0 8 * * 1'  # Weekly Monday 08:00 UTC — smoke tests
+  workflow_dispatch:
 
 jobs:
-  check:
+  # ── Fast gate: typecheck + build ──
+  build:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -15,6 +19,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: '22'
+          cache: 'npm'
 
       - name: Install dependencies
         run: npm ci
@@ -24,3 +29,54 @@ jobs:
 
       - name: Build
         run: npm run build
+
+  # ── Unit tests (vitest shard) ──
+  unit-test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        shard: [1, 2]
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Run unit tests (shard ${{ matrix.shard }}/2)
+        run: npx vitest run src/ --reporter=verbose --shard=${{ matrix.shard }}/2
+
+  # ── Smoke tests (scheduled / manual only) ──
+  smoke-test:
+    if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Setup Chrome + xvfb
+        uses: ./.github/actions/setup-chrome
+        id: setup-chrome
+
+      - name: Build
+        run: npm run build
+
+      - name: Run smoke tests
+        run: |
+          xvfb-run --auto-servernum --server-args="-screen 0 1280x720x24" \
+            npx vitest run tests/smoke/ --reporter=verbose
+        env:
+          OPENCLI_BROWSER_EXECUTABLE_PATH: ${{ steps.setup-chrome.outputs.chrome-path }}
+    timeout-minutes: 15

.github/workflows/e2e-headed.yml

@@ -0,0 +1,37 @@
+name: E2E Headed Chrome
+
+on:
+  push:
+    branches: [main, dev]
+  pull_request:
+    branches: [main, dev]
+  workflow_dispatch:
+
+jobs:
+  e2e-headed:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Setup Chrome + xvfb
+        uses: ./.github/actions/setup-chrome
+        id: setup-chrome
+
+      - name: Build
+        run: npm run build
+
+      - name: Run E2E tests (headed Chrome + xvfb)
+        run: |
+          xvfb-run --auto-servernum --server-args="-screen 0 1280x720x24" \
+            npx vitest run tests/e2e/ --reporter=verbose
+        env:
+          OPENCLI_BROWSER_EXECUTABLE_PATH: ${{ steps.setup-chrome.outputs.chrome-path }}