Fix node planning for interface fragments with non-Node implementors

[michaelstaib]

Fixes #10170

[Copilot]

Pull request overview

This PR fixes selection-set partitioning and operation planning when an interface fragment appears inside a node(...) selection set, ensuring implementors that cannot actually occur at runtime (because they are not possible types of the enclosing selection set) are pruned from generated branches/plans.

Changes:

• Update SelectionSetByTypePartitioner to restrict concrete branches to possible types of the enclosing selection set and to additionally filter candidates against all enclosing type conditions.
• Add partitioning tests covering interface fragments where some interface implementors are not possible types of the node field result type, including nested interface fragments.
• Add abstract lookup fanout planning tests + snapshots to ensure non-Node interface implementors are pruned from node fanout branches.

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.Execution.Tests/Planning/SelectionSetByTypePartitionerTests.cs	Adds regression tests for partitioning interface/nested-interface fragments that must not produce branches for impossible runtime types.
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Planning/AbstractLookupFanoutPlanningTests.cs	Adds regression tests to ensure planning prunes non-Node implementors when fanout is derived from an interface fragment inside node(...).
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Planning/snapshots/AbstractLookupFanoutPlanningTests.Plan_Should_Prune_NonNode_Implementor_When_NodeSelectionSet_Has_No_Shared_Selections.yaml	Adds snapshot for pruning behavior when node(...) has only interface-fragment selections (no shared selections).
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Planning/snapshots/AbstractLookupFanoutPlanningTests.Plan_Should_Prune_NonNode_Implementor_When_InterfaceFragment_Is_In_NodeSelectionSet.yaml	Adds snapshot for pruning behavior when node(...) includes shared Node selections plus an interface fragment.
src/HotChocolate/Fusion/src/Fusion.Execution/Planning/Partitioners/SelectionSetByTypePartitioner.cs	Fixes branch generation for interface selections by intersecting with enclosing possible types/type conditions to avoid impossible branches.

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Patch coverage

100.0% of changed lines covered (23/23)

File	Covered	Changed	Patch %
…/Planning/Partitioners/SelectionSetByTypePartitioner.cs	23	23	100.0% 🟢

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Project coverage: 54.0% (237560/439953 lines)