🤖 ci: optimize Playwright installation with caching and Docker

Addresses slow/flaky CI caused by apt mirror issues during Playwright
browser installation.

## Changes

### Storybook tests - Use Docker container (eliminates apt entirely)
- Run in mcr.microsoft.com/playwright:v1.56.0-noble container
- All browser dependencies are pre-installed in the image
- No apt-get calls needed, immune to mirror issues

### E2E tests - Use caching + retry logic
- Cache ~/.cache/ms-playwright keyed by Playwright version
- On cache hit: only run install-deps (apt for system libs)
- On cache miss: run install --with-deps (download + apt)
- Add retry logic (3 attempts with 10s delay) for apt flakiness
- Install only chromium (sufficient for Electron tests)

## Why not Docker for E2E?
E2E tests run Electron which requires xvfb and host display access,
making containerization complex. The cache + retry approach handles
the apt issue for this case.

## Expected Impact
| Job | Before | After |
|-----|--------|-------|
| Storybook | apt flaky, 3-5 min | No apt, ~1 min |
| E2E (cache hit) | apt flaky | apt with retry |
| E2E (cache miss) | apt flaky, all browsers | apt with retry, chromium only |

_Generated with `mux`_

Author: ammar-agent

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

@@ -0,0 +1,48 @@
+name: "Setup Playwright"
+description: "Install Playwright browsers and dependencies with caching"
+inputs:
+  browsers:
+    description: "Space-separated list of browsers to install (e.g., 'chromium', 'chromium webkit')"
+    required: false
+    default: "chromium"
+runs:
+  using: "composite"
+  steps:
+    - name: Get Playwright version
+      id: playwright-version
+      shell: bash
+      run: |
+        # Extract Playwright version from bun.lock
+        VERSION=$(grep -A1 '"playwright":' bun.lock | grep -oP '"\K[0-9]+\.[0-9]+\.[0-9]+' | head -1)
+        echo "version=$VERSION" >> $GITHUB_OUTPUT
+        echo "Playwright version: $VERSION"
+
+    - name: Cache Playwright browsers
+      id: cache-playwright
+      uses: actions/cache@v4
+      with:
+        path: ~/.cache/ms-playwright
+        key: ${{ runner.os }}-playwright-${{ steps.playwright-version.outputs.version }}-${{ inputs.browsers }}
+        restore-keys: |
+          ${{ runner.os }}-playwright-${{ steps.playwright-version.outputs.version }}-
+
+    - name: Install Playwright browsers and dependencies
+      shell: bash
+      run: |
+        if [[ "${{ steps.cache-playwright.outputs.cache-hit }}" == "true" ]]; then
+          echo "Cache hit - installing only system dependencies"
+          # Retry logic for apt which can be flaky with Azure mirrors
+          for i in 1 2 3; do
+            bun x playwright install-deps ${{ inputs.browsers }} && break
+            echo "Attempt $i failed, retrying in 10s..."
+            sleep 10
+          done
+        else
+          echo "Cache miss - installing browsers and dependencies"
+          # install --with-deps downloads browsers AND installs system deps in one command
+          for i in 1 2 3; do
+            bun x playwright install --with-deps ${{ inputs.browsers }} && break
+            echo "Attempt $i failed, retrying in 10s..."
+            sleep 10
+          done
+        fi

.github/workflows/ci.yml

@@ -126,6 +126,10 @@ jobs:
     name: Storybook Interaction Tests
     runs-on: ${{ github.repository_owner == 'coder' && 'depot-ubuntu-22.04-16' || 'ubuntu-latest' }}
     if: github.event.inputs.test_filter == ''
+    # Use Playwright Docker image - has all browser deps pre-installed, no apt needed
+    container:
+      image: mcr.microsoft.com/playwright:v1.56.0-noble
+      options: --user 1001
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -134,9 +138,6 @@ jobs:
 
       - uses: ./.github/actions/setup-mux
 
-      - name: Install Playwright browsers
-        run: bun x playwright install --with-deps
-
       - name: Build Storybook
         run: make storybook-build
 
@@ -160,16 +161,12 @@ jobs:
 
       - uses: ./.github/actions/setup-mux
 
-      - name: Install system dependencies
+      - name: Install xvfb
         run: |
           sudo apt-get update
           sudo apt-get install -y xvfb
 
-      - name: Install Playwright runtime dependencies
-        run: bun x playwright install-deps
-
-      - name: Install Playwright browsers
-        run: bun x playwright install --with-deps
+      - uses: ./.github/actions/setup-playwright
 
       - name: Run e2e tests
         run: xvfb-run -a make test-e2e