Expose labeled tuple element declarations in the TypeScript 7 API

[Copilot]

TypeScript 7 did not expose tuple element labels through TupleType, preventing API consumers from recovering foo and bar from:

function gh1449<T extends [foo: any, bar?: any]>(a: T): T;

• API

  • Adds TupleType.labeledElementDeclarations.
  • Represents declarations as project-scoped NodeHandle<NamedTupleMember | ParameterDeclaration> values.

• Protocol

  • Serializes labeled declarations only on tuple targets.
  • Preserves undefined entries for partially labeled tuples.

• Coverage

  • Exercises label retrieval and node resolution through both async and sync APIs.

• Fixes [API] labeledElementDeclarations is missing in TypeScript 7 #64105