Avoid redundant source row decodes in Fusion value completion

[michaelstaib]

No description provided.

[Copilot]

Pull request overview

This PR optimizes Fusion execution result value completion by introducing a stack-only “snapshot” of SourceResultElement that carries the already-decoded metadata row (DbRow), reducing redundant row lookups during completion and leaf assignment. It also adds regression coverage around enum masking behavior.

Changes:

• Added SourceResultElementSnapshot to cache decoded DbRow metadata for a SourceResultElement.
• Updated ValueCompletion and composite result assignment paths to use snapshots for scalar/enum handling and leaf writes.
• Extended SourceResultDocument APIs to accept DbRow directly and added tests for enum masking in edge cases.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Execution/Results/FetchResultStoreTests.cs	Adds tests ensuring enum values are masked when unknown or when encoded with JSON escape sequences.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElementSnapshot.cs	Introduces a ref-struct snapshot type carrying _row to avoid repeated row decoding.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.cs	Adds CreateSnapshot() factory to produce snapshots from elements.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultDocument.Text.cs	Adds DbRow-based overloads for string/raw-value accessors used by snapshots.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultDocument.cs	Adds DbRow-based overloads for array/object metadata queries.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/CompositeResultElement.cs	Updates leaf assignment to accept a snapshot instead of (element,row) pairs.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/CompositeResultDocument.cs	Refactors source assignment to accept (SourceResultDocument, Cursor, DbRow) to leverage snapshots.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/ValueCompletion.cs	Switches completion logic to create and pass snapshots, reducing repeated DbRow fetches.

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