[Fusion] Fix introspection argument list misalignment

[glen-84]

Summary

• The gateway introspection resolvers __Field.args and __Directive.args sized their result list to the non-deprecated argument count but iterated the list slots while indexing the full argument list, skipping deprecated arguments with continue. A deprecated argument that was not last left an unfilled list slot, which surfaced as an "Unexpected Execution Error" and dropped a trailing argument.
• Both resolvers now iterate the source arguments and advance the list enumerator only for the arguments they include, matching the existing enumValues and inputFields resolvers.

Test plan

• New gateway introspection test: a field whose first argument is deprecated and second is not; __type.fields.args returns only the non-deprecated argument (previously errored).
• Full Fusion.Execution.Tests suite passes.

[Copilot]

Pull request overview

Fixes a gateway introspection bug where __Field.args / __Directive.args could leave gaps in the produced list when deprecated arguments were skipped, causing an execution error and dropping subsequent arguments.

Changes:

• Update __Field.Arguments and __Directive.Arguments to iterate source arguments and advance the result-list enumerator only for included entries (avoids index/list-slot misalignment).
• Add a regression test covering the “deprecated arg first, non-deprecated arg second” scenario via gateway introspection.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Execution/Introspection/FieldArgumentsIntrospectionTests.cs	Adds regression coverage ensuring deprecated args are excluded without producing list gaps/errors.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Introspection/__Field.cs	Fixes __Field.args list materialization to avoid gaps when skipping deprecated args.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Introspection/__Directive.cs	Fixes __Directive.args list materialization to avoid gaps when skipping deprecated args.

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[github-actions]

Patch coverage

57.1% of changed lines covered (8/14)

File	Covered	Changed	Patch %
…/src/Fusion.Execution/Execution/Introspection/__Directive.cs	4	7	57.1% 🔴
…/src/Fusion.Execution/Execution/Introspection/__Field.cs	4	7	57.1% 🔴

Uncovered changed lines (JSON)

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  "sha": "4611aa28ac1a11e3ab333b36cbe967d024e834c3",
  "files": [
    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Introspection/__Directive.cs", "ranges": [[167, 169]] },
    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Introspection/__Field.cs", "ranges": [[90, 92]] }
  ]
}

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Project coverage: 52.5% (216951/413145 lines)