test(zod): compile generated schema text

[robgruen]

Summary

• Collect schema text emitted by the existing Zod tests and type-check it together with the installed TypeScript compiler using strict and noEmit.
• Compile each snippet as a separate module so repeated test type names do not collide and named references remain intact.
• Preserve the existing regex assertions, include getSchemaText() output, and clean up temporary files on success and failure.
• Add negative controls for invalid tuple syntax and unresolved type references.
• Document the compiler-backed checks in the TypeScript README.

Context

This implements the compiler-validation suggestion from the review of #445. It is based on main and does not duplicate that PR's precedence fix or regression tests. The shared schema helper will also collect and compile #445's new test output when that PR merges.

Validation

• npm run build: passed.
• Local TypeScript compiler, tsc -p test: passed.
• node --test --test-reporter=spec out\zod.test.js: 51 tests passed, including both negative controls and the batch compilation hook.
• git diff --check: passed.

Local validation used Windows, TypeScript 7.0.2, and Node 22.18.0. The local Node version is slightly below the package's >=22.19.0 requirement; supported-version CI should still run before merging.