Add E2E integration tests for AI detection flow

[Edmon02]

Description

Expand test coverage with end-to-end integration tests that exercise the full AI detection pipeline.

Proposed Tests

• Provider integration: Mock LLM responses and verify the full scan → detect → cache → remove flow
• Options page UI: Puppeteer/Playwright tests for the AI settings tab (key entry, model search, save/load)
• Content script injection: Verify ai-scanner.js and video-ad-interceptor.js are injected correctly
• Empty space collapse: Load pages with ad-like structures and verify DOM cleanup
• Video ad bypass: Test main-world patch against mock player instances

Current Coverage

62 unit tests pass across 4 AI modules. Integration/E2E tests are missing.

Labels

testing, ai-detection