[Fusion] Resolve abstract types from raw UTF-8 type names for small implementer sets

[michaelstaib]

No description provided.

[Copilot]

Pull request overview

This PR optimizes abstract type resolution during value completion by avoiding string allocations when resolving __typename for small possible-type sets, using raw UTF-8 comparisons.

Changes:

• Added SourceResultElement.TryGetRawStringValue(...) to expose raw UTF-8 bytes for non-escaped JSON strings.
• Cached UTF-8 encoded type names on FusionObjectTypeDefinition (Utf8Name) for allocation-free comparisons.
• Updated ValueCompletion.GetType(...) to resolve abstract types via raw UTF-8 __typename matching for up to 8 candidates, with a fallback to the existing string-based lookup.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.cs	Adds an API to retrieve raw UTF-8 bytes for simple JSON string values.
src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/ValueCompletion.cs	Uses raw UTF-8 __typename to resolve abstract types for small implementer sets; narrows schema usage to fusion schema.
src/HotChocolate/Fusion/src/Fusion.Execution.Types/FusionObjectTypeDefinition.cs	Stores a pre-encoded UTF-8 name to enable allocation-free type-name matching.

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[github-actions]

Patch coverage

94.0% of changed lines covered (94/100)

File	Covered	Changed	Patch %
…/src/Fusion.Execution/Text/Json/SourceResultDocument.Text.cs	22	27	81.5% 🟡
…/src/Fusion.Execution/Execution/Results/ValueCompletion.cs	53	54	98.1% 🟡
…/src/Fusion.Execution.Types/FusionInterfaceTypeDefinition.cs	9	9	100.0% 🟢
…/src/Fusion.Execution/Execution/Nodes/OperationCompiler.cs	6	6	100.0% 🟢
…/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.cs	4	4	100.0% 🟢

Uncovered changed lines (JSON)

{
  "sha": "38e2c436121fa9c6484549603740375bd78c7b8d",
  "files": [
    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultDocument.Text.cs", "ranges": [[53, 57]] },
    { "path": "src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/ValueCompletion.cs", "ranges": [[1128, 1128]] }
  ]
}

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Project coverage: 53.4% (227570/426362 lines)