Embedded browser

[weiran]

Summary

• introduce the custom embedded browser experience (glass controls, reload/stop, comments sheet behavior)
• rename the Onboarding module and APIs to WhatsNew across app/data/domain/tests
• update WhatsNew storage key and first‑install gating
• refresh settings wiring and test runner module names

Testing

• ./run_tests.sh (WhatsNew + Settings failed before fix; rerun recommended)

Summary by CodeRabbit

• New Features

  • “What’s New” walkthrough added.
  • Built‑in post link browser with integrated comments drawer.
  • New CommentRow and PostRow UI components.

• Improvements

  • Link browser modes introduced (in‑app, custom, system).
  • Configurable post display: title line limit and thumbnail sizing.
  • New pill UI for votes, comments and bookmarks.
  • Smoother navigation and link‑opening flows.

• Tests

  • Added WhatsNew tests; onboarding tests removed.

• Chores

  • .build-device added to .gitignore.