ci: add strict GitHub Actions workflow

[sergdort]

Summary

• add strict GitHub Actions CI workflow for PRs and pushes to main
• enforce format, lint, test, and web build checks on ubuntu-latest
• fix TTS panel lint issues with real code changes including captions track
• add README CI section with local pre-push gate command
• apply repo formatting updates required for a green strict gate

Validation

• pnpm run format:check
• pnpm run lint
• pnpm run test
• pnpm --dir apps/web build