[Fusion] Fix deferred fragments losing type conditions on composite fields

[tobias-tengler]

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[Copilot]

Pull request overview

This PR fixes a Fusion defer planning bug where composite fields selected under a type condition could lose that type condition when reconstructing incremental plan operations (leading to invalid subgraph operations when the enclosing parent is abstract-typed).

Changes:

• Track the active type condition name on FieldPathSegment when entering composite fields during defer occurrence collection.
• When rebuilding incremental plan operations, re-wrap composite fields in an ... on <Type> inline fragment when the path segment indicates a type condition.
• Add a regression test and snapshot covering a Node (abstract) parent with deferred fragments and a deferred composite field requiring an entity lookup across subgraphs.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/DeferTests.cs	Adds a regression test exercising deferred composite fields under a type condition on an abstract parent.
src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/snapshots/DeferTests.Defer_Composite_Field_Under_Type_Condition_On_Abstract_Parent_Is_Wrapped.yaml	Snapshot proving the reconstructed deferred operations preserve the type condition wrapping.
src/HotChocolate/Fusion/src/Fusion.Execution/Planning/FieldPathSegment.cs	Extends path segments to carry an optional TypeCondition for later reconstruction.
src/HotChocolate/Fusion/src/Fusion.Execution/Planning/DeferOperationRewriter.cs	Re-wraps reconstructed composite fields in inline fragments based on the stored path segment type condition.
src/HotChocolate/Fusion/src/Fusion.Execution/Planning/DeferOccurrenceCollector.cs	Records the active type condition name onto composite path segments during traversal.

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Patch coverage

100.0% of changed lines covered (16/16)

File	Covered	Changed	Patch %
…/src/Fusion.Execution/Planning/DeferOccurrenceCollector.cs	2	2	100.0% 🟢
…/src/Fusion.Execution/Planning/DeferOperationRewriter.cs	13	13	100.0% 🟢
…/Fusion/src/Fusion.Execution/Planning/FieldPathSegment.cs	1	1	100.0% 🟢

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Project coverage: 52.5% (217101/413261 lines)