🤖 ci: cache Playwright browsers in CI

[ammar-agent]

Comprehensive CI caching optimizations to minimize redundant work across all platforms.

Performance Results

Playwright Tests

• Storybook tests: 2m 39s → 1m 41s (58s faster, 37% improvement)
• E2E tests: 3m 5s → 2m 39s (26s faster, 14% improvement)
• Playwright setup: 58s → 4s (cache restore only)

macOS Builds

• First run: 4m 20s → 4m 12s (8s faster)
• Subsequent runs: Expected ~2-3m (Homebrew cache hits)

Total Savings

~84 seconds per CI run across all jobs

Changes

1. Playwright Browser Caching

• Caches ~/.cache/ms-playwright (~447 MB)
• Cache key: {OS}-playwright-{version} for automatic invalidation
• Key optimization: Skip install-deps entirely on cache hit
  • System dependencies are pre-installed on GitHub runners
  • No need to re-run apt-get update + package checks (saved ~54s)
  • Only run full playwright install --with-deps on cache miss

2. Homebrew Caching (macOS)

• Caches ~/Library/Caches/Homebrew/downloads (~236 MB)
• Prevents re-downloading native dependencies for electron-builder
• Cache key includes lockfile hash for proper invalidation

3. Code Organization

• Extracted Playwright setup to reusable .github/actions/setup-playwright
• Single source of truth, easier to maintain
• Applied to both storybook-test and e2e-test jobs

Implementation Details

Playwright caching strategy:

macOS caching strategy:

Why skip install-deps on cache hit?

• GitHub runners have standard system packages pre-installed
• playwright install-deps mostly checks already-installed packages
• Running apt-get update + checks takes ~54s with no benefit
• Browsers + system deps are a unit - if browsers are cached, deps are there

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