Resolve resident browser proxy CDP

[miguelg719]

Summary

• resolve Chromium through a /json/version endpoint
• validate the configured proxy origin and returned loopback browser WebSocket URL
• rewrite only scheme and authority while preserving the exact browser target path and query
• use a bounded fetch timeout and the existing raw browser WebSocket CDP transport

Scope

Stack 2/6, based on the init-first protocol PR. This PR adds a separately testable transport resolver only; worker startup wiring lands later in the stack. Public builds remain unconfigured, with no compatibility negotiation, fallback, or public-connect behavior.

Validation

• success, malformed JSON, missing/invalid URL, HTTP failure, and timeout tests
• default-port, secure-WebSocket, escaped-path, and repeated-query preservation
• complete server suite on this branch
• complete TypeScript/package/rule suite at the stack tip

[changeset-bot]

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Latest commit: d59ecef

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[cubic-dev-ai]

All reported issues were addressed across 2 files

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