fix: clone fields array in buildClassMetadata to prevent FieldResolver metadata leak into dual-type InputType

[Copilot]

• Add a @Mutation using DualClassInput as argument so the InputType is reachable in the schema
• Assert DualClass ObjectType contains the computed field resolver
• Assert DualClassInput InputType does NOT contain the computed field resolver
• All 113 tests in resolvers.ts pass

[Copilot]

Pull request overview

Fixes a metadata-mutation bug in MetadataStorage that affects “dual-type” classes (decorated with both @ObjectType() and @InputType()), where later @FieldResolver processing could accidentally mutate a shared fields array and leak resolver fields into the InputType, leading to CannotDetermineGraphQLTypeError during schema build.

Changes:

• Clone the cached fields array when assigning it to each class metadata definition to avoid cross-definition mutation.
• Add a functional regression test that reproduces the dual-type + external @FieldResolver scenario and asserts schema building succeeds.

Reviewed changes

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

File	Description
src/metadata/metadata-storage.ts	Prevents fields array reference sharing across object/input definitions by cloning on assignment.
tests/functional/resolvers.ts	Adds a regression test ensuring external field resolvers don’t leak into @InputType() fields for dual-decorated classes.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.

[MichalLytek]

@copilot add new entry to the changelog.md, in the unreleased section