Upgrade/ts6 yarn4

[alexeyslynko]

Summary

Migrate the monorepo tooling to Yarn 4 and TypeScript 6.0.3 without changing published package versions.

Changes

• Add Yarn 4 configuration with nodeLinker: node-modules.
• Pin TypeScript to 6.0.3 and update compiler options for TS 6 compatibility.
• Add package-level rootDir settings to keep generated lib output layout stable.
• Upgrade Jest tooling for TypeScript 6.
• Fix TS 6 compatibility issues in class members and chained decorators.
• Make REST endpoint handling tolerate empty successful responses.
• Make model update object detection work with cross-realm/fetch JSON objects.
• Refresh scoped @type-r/* import examples in docs and examples.
• Rebuild tracked lib/dist and generated docs artifacts.

Package versions

This PR intentionally keeps package versions unchanged:

• @type-r/models: 4.1.0
• @type-r/react: 4.1.0
• @type-r/endpoints: 4.0.2

Verification

• COREPACK_HOME=/tmp/corepack corepack yarn tsc --version
  • Version 6.0.3
• COREPACK_HOME=/tmp/corepack corepack yarn build:all
  • passed
• COREPACK_HOME=/tmp/corepack corepack yarn test
  • QUnit: 201/201 passed
  • Jest: 15/15 suites passed
  • Jest tests: 238/238 passed