Fix SchemaParameter.schema type in openapi-3-1 (OasSchema32 -> OasSchema31)

[tarunagnihotri534]

Summary

Fixes a typing error in openapi-3-1/index.d.ts where SchemaParameter.schema was typed as OasSchema32 instead of OasSchema31.

Root Cause

SchemaParameter was copied over from openapi-3-2/index.d.ts in commit a52c3d0 ("OpenApi type improvements") and the schema type was never switched back to the 3.1 one. OasSchema32 isn't declared or imported in openapi-3-1/index.d.ts, so anyone type-checking declaration files with skipLibCheck: false hits this error when importing from @hyperjump/json-schema/openapi-3-1:

openapi-3-1/index.d.ts(230,11): error TS2552: Cannot find name 'OasSchema32'. Did you mean 'OasSchema31'?

It went unnoticed because the repo's tsconfig.json has skipLibCheck: true and no .ts file imports SchemaParameter, so npm run check-types never looked at it.

Changes

• Changed SchemaParameter.schema from OasSchema32 to OasSchema31, matching MediaType.schema and Header.schema in the same file.
• Added openapi-3-1/index.spec.ts, a small type-level regression test that imports Parameter and SchemaParameter, so npm run check-types now exercises these types.

Testing

Added openapi-3-1/index.spec.ts (Vitest expectTypeOf), with two tests:

• SchemaParameter["schema"] is not any and is exactly OasSchema31.
• The public Parameter union exposes the same OasSchema31 type for its schema variants.

Because the bug lives in a .d.ts file, the test is checked at compile time by npm run check-types, not at runtime. Before the fix, the unresolved OasSchema32 is treated as any, so the type check fails:

openapi-3-1/index.spec.ts(8,51): error TS2349: This expression is not callable.
  Type 'Inverted<ExpectAny<OasSchema32>>' has no call signatures.

To run it locally:

npm run check-types
npm test

Verification

• npm run check-types fails on the unfixed code and passes with the fix.
• npm test passes (29 test files, 15,003 tests) and eslint reports no errors.
• Compiling openapi-3-1/index.d.ts with --skipLibCheck false no longer reports the OasSchema32 error. The remaining errors from @hyperjump/browser are unrelated and out of scope here.

Fixes #135