Fix composite field must have selection set rule

[michaelstaib]

No description provided.

[Copilot]

Pull request overview

This PR fixes validation of the GraphQL “leaf field selections” rule so composite fields wrapped in list/non-null types correctly require a selection set (notably affecting introspection fields like types { ofType } and fields { type }), and adds regression coverage in Fusion ASP.NET Core tests.

Changes:

• Unwrap parent types in LeafFieldSelectionsRule before looking up fields, ensuring wrapped composite parent types are validated correctly.
• Add two new Fusion gateway introspection regression tests plus their snapshot baselines for missing selection sets.
• Default Fusion test gateway hosting environment to Development to avoid environment-driven security behavior interfering with tests.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/HotChocolate/Core/src/Validation/Rules/LeafFieldSelectionsRule.cs	Unwraps parentType via NamedType() before validating field selections.
src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/IntrospectionTests.cs	Adds regression tests for introspection composite fields without selection sets.
src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/FusionTestBase.cs	Injects a default IHostEnvironment (Development) for gateway test servers.
src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/snapshots/IntrospectionTests.Introspection_OfType_Without_SelectionSet.yaml	Snapshot baseline for ofType missing selection set error.
src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/snapshots/IntrospectionTests.Introspection_Field_Type_Without_SelectionSet.yaml	Snapshot baseline for type missing selection set error.

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