Polish panel scale and runtime QA

[heznpc]

Summary

• Increase AcademyLens panel scale, typography, spacing, and touch targets so the floating card feels less undersized on Academy pages.
• Add hidden runtime version markers to the panel host and panel element to make stale unpacked-extension reload issues easier to diagnose.
• Tighten E2E visual smoke thresholds for panel width, font size, control height, and version parity with manifest.json.

Validation

• npx playwright test tests/e2e/academy-lens.spec.js -g "panel has viewport-safe visual smoke"
• npm run format:check
• npm run check:full

Browser QA

• Opened a logged-in OpenAI Academy courses page in Chrome.
• Confirmed the extension panel attaches and the page has no captured console warnings/errors.
• Chrome policy blocks direct chrome://extensions reload automation, so the live browser was still running the previously loaded unpacked extension until manually reloaded.