[@typescript/api] Add a few more checker APIs

[andrewbranch]

• isContextSensitive
• getReturnTypeOfSignature
• getRestTypeOfSignature
• getTypePredicateOfSignature
• getBaseTypes
• getPropertiesOfType
• getIndexInfosOfType
• getConstraintOfTypeParameter
• getTypeArguments

[Copilot]

Pull request overview

Adds several additional TypeScript checker APIs to the @typescript/api surface by wiring new RPC methods through the Go API server and exposing them via the sync/async TypeScript client wrappers (with accompanying tests and enum generation).

Changes:

• Add new checker RPC endpoints (e.g. isContextSensitive, signature/type queries) and snapshot signature-handle resolution on the Go server.
• Expose new APIs and types in the TypeScript sync/async clients (including TypePredicate/IndexInfo) and generate TypePredicateKind.
• Add sync + async API tests covering the new checker endpoints.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/checker/types.go	Adds exported getters for TypePredicate and IndexInfo to support API serialization.
internal/checker/exports.go	Exposes additional checker methods via exported wrappers used by the API server.
internal/api/session.go	Adds signature-handle resolution and implements new checker request handlers + dispatch entries.
internal/api/proto.go	Adds new method IDs, request param types, and response shapes for new checker RPCs.
_packages/api/src/sync/types.ts	Adds TypePredicate and IndexInfo public type definitions for sync client.
_packages/api/src/async/types.ts	Adds TypePredicate and IndexInfo public type definitions for async client.
_packages/api/src/sync/api.ts	Adds new Checker methods and exports TypePredicateKind + related types (sync).
_packages/api/src/async/api.ts	Adds new Checker methods and exports TypePredicateKind + related types (async).
_packages/api/src/proto.ts	Adds TS-side protocol response typings for TypePredicateResponse and IndexInfoResponse.
_packages/api/src/enums/typePredicateKind.ts	Adds generated runtime enum for TypePredicateKind.
_packages/api/src/enums/typePredicateKind.enum.ts	Adds generated TypeScript enum TypePredicateKind.
_packages/api/test/sync/api.test.ts	Adds sync tests covering newly added checker APIs.
_packages/api/test/async/api.test.ts	Adds async tests covering newly added checker APIs.
Herebyfile.mjs	Hooks TypePredicateKind into enum generation pipeline.