Model extension file access in Chrome E2E

[YUMA-NAGAO]

Summary

• Keep the existing file-origin access flag used by the browser fixtures.
• Add Chromium's extension-specific test switch so E2E runs model the user-enabled Allow access to file URLs setting.
• Keep runtime code, manifest permissions, and product behavior unchanged.

Why

The E2E suite loads file:// fixtures, but --allow-file-access-from-files does not disable Chromium's separate user opt-in check for extensions injecting into file URLs. --disable-extensions-file-access-check is Chromium's test switch for that extension-specific permission path.

Chromium source: https://chromium.googlesource.com/chromium/src/+/main/chrome/common/chrome_switches.cc

Testing

• npm ci
• npm run lint
• npm run build:release
• npm test (43 files, 534 tests)
• npm run test:e2e -- basic (10/10 passed)
• Codex second-opinion review (no actionable findings)

GitHub Actions

The upstream CI run is awaiting repository-maintainer approval for a workflow from a fork. GitHub has not started any jobs yet: https://github.com/igrigorik/videospeed/actions/runs/30735334595

Notes

• One file changed; no production code or manifest permissions changed.
• Both flags are retained because they model separate file-origin and extension opt-in checks.