Fixes #2111.

What changed

• Convert TSError instances crossing the ESM loader worker boundary into a serializable Error copy.
• Apply that conversion during loader registration and from the ESM loader hooks, so config and compile diagnostics survive Node's loader-worker serialization.
• Add a regression fixture with an intentionally invalid tsconfig.json and assert the ESM loader prints the real TypeScript diagnostic instead of [Object: null prototype].

Verification

• Red test before the fix: YARN_ENABLE_GLOBAL_CACHE=false YARN_CACHE_FOLDER=/tmp/ts-node-2111-yarn-cache YARN_NM_MODE=classic yarn test-spec ./dist/test/esm-loader.spec.js --match '*reports invalid tsconfig diagnostics from the ESM loader*'
• YARN_ENABLE_GLOBAL_CACHE=false YARN_CACHE_FOLDER=/tmp/ts-node-2111-yarn-cache YARN_NM_MODE=classic yarn build-tsc
• YARN_ENABLE_GLOBAL_CACHE=false YARN_CACHE_FOLDER=/tmp/ts-node-2111-yarn-cache YARN_NM_MODE=classic yarn lint
• YARN_ENABLE_GLOBAL_CACHE=false YARN_CACHE_FOLDER=/tmp/ts-node-2111-yarn-cache YARN_NM_MODE=classic yarn test-spec ./dist/test/esm-loader.spec.js --match '*reports invalid tsconfig diagnostics from the ESM loader*'
• YARN_ENABLE_GLOBAL_CACHE=false YARN_CACHE_FOLDER=/tmp/ts-node-2111-yarn-cache YARN_NM_MODE=classic yarn test-spec ./dist/test/esm-loader.spec.js --match '*should throw type errors without transpile-only enabled*'
• YARN_ENABLE_GLOBAL_CACHE=false YARN_CACHE_FOLDER=/tmp/ts-node-2111-yarn-cache YARN_NM_MODE=classic yarn test-spec ./dist/test/diagnostics.spec.js
• git diff --check

I also tried the full esm-loader.spec.js file locally, but the Node 24.15.0 runtime trips several existing expectations unrelated to this change, including source-map line expectations, import-assertion syntax, and deprecation-warning stderr assertions.