Add regression coverage for dependencies in schemas without $schema

[Copilot]

Schemas that omit $schema now default to modern draft handling, which raised the risk of legacy dependencies being silently skipped. Existing coverage only checked explicit draft behavior, leaving the undeclared-schema path untested.

• Problem

  • Add coverage for the backward-compatibility case where a schema uses legacy dependencies without declaring $schema.
  • Ensure the default jsonDoc.validate(...) path continues to honor dependencies for both property-array and schema forms.

• Test coverage

  • Extend existing parser tests to validate legacy dependencies through the inferred-draft path instead of only the helper that forces an explicit draft.
  • Cover both legacy shapes:
    • dependencies: { a: ['b'] }
    • dependencies: { a: { ...subschema... } }

• Intent made explicit

  • Introduce a small test helper for the inferred-draft validation path so the regression target is clear in the test body.

function validateWithInferredDraft(jsonDoc: JSONDocument, textDoc: TextDocument, schema: JSONSchema) {
	return jsonDoc.validate(textDoc, schema);
}