Stabilize ReadCursor E2E pipeline across local and GitHub Actions

[RupanPrasai]

Summary

This PR fixes the current E2E regressions by hardening Chrome session startup, removing brittle extension-id scraping, and adding a reliable MV3 service-worker handshake before E2E injection.

What changed

1) CI/session stability for WDIO + Chrome

• Updated client/tests/e2e/config/wdio.browser.conf.ts to:
  • Use robust CI Chrome args (--no-sandbox, --disable-dev-shm-usage, --disable-gpu, --headless=new in CI).
  • Keep extension runs single-instance (maxInstances: 1) to avoid profile contention.
  • Use a unique --user-data-dir per run.
  • Emit debug logs for Chrome binary/version, chromedriver version, args, profile dir, unpack dir, and deterministic extension id.
  • Write WDIO logs to tests/e2e/.tmp/wdio-logs for artifact collection.

2) Deterministic extension ID (no chrome://extensions scraping)

• Added E2E-only manifest key injection in client/chrome-extension/manifest.ts:
  • key is set only for E2E builds (version_name contains -e2e).
  • tabs permission is added only in E2E builds.
• Replaced Chrome extension path resolver implementation in client/tests/e2e/utils/extension-path.ts:
  • It now builds chrome-extension://<deterministic-id> directly from the computed id passed by WDIO.
  • Removed all chrome://extensions DOM scraping logic.
• In WDIO config, derive deterministic id from manifest key and wire it into browser.getExtensionPath().

3) Reliable MV3 service-worker wake/handshake

• Added an E2E-only E2E_PING message in client/chrome-extension/src/background/index.ts.
• Added waitForE2EBackgroundReady() retry/backoff handshake in client/tests/e2e/helpers/readcursor.ts and run it before RC_E2E_INJECT.
• Updated blocked-page spec to use the shared injection helper so it benefits from the same handshake/retry behavior.

4) GitHub Actions E2E workflow

• Enabled and updated .github/workflows/e2e.yml:
  • Runs on PR + manual dispatch.
  • Installs Chrome and logs browser/driver versions.
  • Builds E2E extension variant (cross-env CLI_CEB_E2E=true pnpm zip).
  • Runs only the E2E package with single concurrency.
  • Uploads E2E artifacts on failure/success (tests/e2e/.tmp/**, dist-zip/*.zip).

Why this fixes the failures

• panel-controls.test.ts extension path breakage: removed name-based scraping entirely; extension URL is deterministic via E2E key.
• viewport-rebuild.test.ts receiving end does not exist: test harness now waits until background SW responds before sending inject trigger.
• GitHub Actions Chrome startup failures: stabilized Chrome launch args/profile handling and constrained extension runs to single instance while improving startup diagnostics.

Validation

• Local command execution was attempted, but pnpm bootstrap failed in this environment due network/proxy restrictions while Corepack tried downloading pnpm@10.11.0.
• The workflow now includes richer logs/artifacts to make CI validation and debugging deterministic.

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