[M4] Config & Visual Map Extensions for playwright_test

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Milestone 4 — Playwright Test Video Integration | Priority: Medium | COMPLETED in PR #27

Extended Config with playwright_test_config block and sync_playwright_after_timestamps pipeline option.

playwright_test:
  framework: pytest
  test_dir: tests/e2e/
  video_dir: test-results/videos/
  trace_dir: test-results/traces/
  min_speed_factor: 0.25
  max_speed_factor: 4.0

Implemented in src/docgen/config.py. See issues/playwright-test-integration/05-config-visual-map.md.