Add generated alias client codegen

[pirate]

Summary

• add generic generated alias client support for TypeScript, Python, and Go
• generate typed browser/page/locator-style alias objects from an external alias manifest, including sticky object wrapping and response unwrapping
• keep ModCDP core generic: Stagehand-specific commands and SDK shapes are supplied only through generated fixtures/manifests
• preserve native ModCDP/CDP surfaces on generated clients while layering generated alias objects on top
• add generated-client live test fixtures for JS, Python, and Go that exercise the public generated client shape against a real browser
• keep generated Stagehand fixture outputs derived from a local manifest so ModCDP does not own Stagehand protocol definitions

Why

Go cannot dynamically register new typed methods at runtime, so the generated Go client is the strictest model for the public shape. This PR follows that constraint across languages: generated clients statically expose the end-user alias objects and typed params/results, while ModCDP remains responsible only for generic transport, validation, routing, and alias-object mechanics.

Validation

• pnpm run lint

The lint run covered formatting, TypeScript, generated-client build, Python ty/pyright, Go formatting/build, and repository hygiene hooks. Live tests were not rerun for this PR update; CI should run tests.