[UM-CLONE-6] Puppeteer — stable CDP-level primitives we can re-export

[Delqhi]

Source

• Project: Puppeteer
• License: Apache-2.0
• Clone mode: code

Feature we want

Puppeteer's Page, Frame, Browser API patterns are the most battle-tested in the ecosystem. We mirror the parts that don't conflict with Playwright's surface.

Why we want it

Lowers learning curve for the millions of devs who already know Puppeteer.

Acceptance criteria

• Compatibility wrapper src/compat/puppeteer.ts exposing puppeteer-shaped API
• Documented in docs/migration-from-puppeteer.md
• Smoke tests for the most-used 20 methods
• PR body cites source repo + commit SHA + license
• THIRD_PARTY_NOTICES.md updated
• Parity test added (proves our clone behaves like source for the relevant case)
• CHANGELOG entry: cloned from Puppeteer@<sha>

Reference

See COMPETITIVE_STRATEGY.md for the full doctrine.