Validate directives on enum values and directive arguments

[glen-84]

Summary

• SchemaValidator publishes directive events for every directives provider it walks, including enum values and directive definition arguments. Directives applied at the ENUM_VALUE and ARGUMENT_DEFINITION (on a directive definition) locations were previously skipped, so rules keyed on DirectiveEvent and DirectiveArgumentAssignmentEvent never saw them — an undefined directive there passed validation silently.

Test plan

• Extended DirectiveIsDefinedRuleTests.Validate_DirectiveIsUndefined_Fails to cover a directive on an enum value and on a directive definition's argument alongside the existing object/field/argument cases.
• HotChocolate.Types.Validation.Tests (404 tests) and HotChocolate.Fusion.Composition.Tests (2848 tests, the only other SchemaValidator consumer) pass on all target frameworks.

[Copilot]

Pull request overview

This pull request updates schema validation so that directives applied to enum values and directive-definition arguments are also validated (via published directive-related validation events), closing a gap where undefined directives at ENUM_VALUE and directive ARGUMENT_DEFINITION locations could previously pass silently.

Changes:

• Publish directive events for IEnumValue members while walking enum values in SchemaValidator.
• Publish directive events for arguments of directive definitions in SchemaValidator.
• Extend DirectiveIsDefinedRuleTests.Validate_DirectiveIsUndefined_Fails to assert failures for undefined directives on an enum value and on a directive definition argument.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/HotChocolate/Core/test/Types.Validation.Tests/Rules/DirectiveIsDefinedRuleTests.cs	Adds coverage for undefined directives on enum values and directive-definition arguments.
src/HotChocolate/Core/src/Types.Validation/SchemaValidator.cs	Publishes directive events for enum values and directive-definition arguments so rules see and validate those directives.

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[github-actions]

Patch coverage

100.0% of changed lines covered (2/2)

File	Covered	Changed	Patch %
…/HotChocolate/Core/src/Types.Validation/SchemaValidator.cs	2	2	100.0% 🟢

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Project coverage: 53.9% (232122/430885 lines)