TypeScript SDK: typed local client and lifecycle API

[SarthakWade]

Scope

Publish a TypeScript SDK generated from or validated against the canonical SDK schema.

The initial API should cover host lifecycle, session lifecycle, navigation, semantic inspection, interactions, waits, capture, diagnostics, capabilities, typed errors, cancellation, and timeouts. It should work in Node.js without requiring a network service.

Constraints

• Use the existing local transport and preserve private socket permissions.
• Do not duplicate protocol validators by hand.
• Keep page-derived strings typed or wrapped as untrusted content.
• Credential operations use aliases and challenge IDs only.
• Child processes are terminated and awaited on cancellation or parent exit.
• Unsupported capabilities return typed failures rather than partial behavior.

Acceptance criteria

• Package build, type checks, lint, unit tests, and integration tests pass.
• Golden fixtures prove request and response parity with the Swift protocol.
• Tests cover missing binary, startup failure, timeout, cancellation, malformed response, protocol mismatch, and host termination.
• API documentation includes minimal CLI-to-SDK migration examples.
• Package contents, license, provenance, and version compatibility are verified before publication.

Blocked by #163.

[yashranaway]

Blocked on #163. Do not handwrite a client that will drift from #169/#170.