Expose Checker.getTypeOfPropertyOfType on the unstable API

[Baptiste Jamin (baptistejamin)]

getTypeOfPropertyOfType already exists on the TypeScript 6 checker and internally in the Go checker (Checker.GetTypeOfPropertyOfType), but it is not wired through typescript/unstable. This PR exports it on the JS API.
It returns the type of a named property, or undefined if the property does not exist. This is the type-level counterpart of getPropertyOfType.

Test plan

• API tests (async + sync): named property types, missing property

[Copilot]

Pull request overview

Exposes Checker.getTypeOfPropertyOfType through the unstable synchronous and asynchronous JavaScript APIs.

Changes:

• Adds protocol dispatch and checker handling.
• Adds sync and async API methods.
• Tests property lookup and missing-property behavior.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tsc/internal/api/session.go	Handles property-type requests.
tsc/internal/api/proto.go	Registers the protocol method.
packages/typescript/src/api/proto.generated.ts	Adds generated protocol typing.
packages/typescript/src/api/sync/api.ts	Exposes the synchronous method.
packages/typescript/src/api/async/api.ts	Exposes the asynchronous method.
packages/typescript/test/sync/api.test.ts	Tests synchronous behavior.
packages/typescript/test/async/api.test.ts	Tests asynchronous behavior.

---

💡 Add a code-review agent skill for context-aware, tailored reviews. Learn more in the docs.