Improve cross-chunk JSON serialization

[michaelstaib]

No description provided.

[Copilot]

Pull request overview

This PR improves how SourceResultDocument writes large scalar values (strings/numbers) that span multiple underlying data chunks by avoiding the “gather into a contiguous scratch buffer” path when JSON output is not indented.

Changes:

• Added JsonWriter.WriteRawValueEnd(JsonTokenType) to finalize multi-chunk raw writes while updating the writer token state.
• Updated SourceResultDocument to stream cross-chunk scalar bytes directly into JsonWriter for minimized output, while keeping the pooled scratch-buffer path for indented output.
• Added tests covering cross-chunk scalar formatting and validating that oversized values fail before writing any output.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/HotChocolate/Json/src/Json/JsonWriter.cs	Adds a raw-write end overload that sets _tokenType for streamed scalar writes.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultDocument.cs	Streams cross-chunk scalar writes in minimized mode; adds max-token-size guard.
src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/ThrowHelper.cs	Adds a helper to throw a consistent ArgumentException for oversized JSON values.
src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Text/Json/SourceResultDocumentTests.cs	Adds tests for cross-chunk scalar output and oversized-value validation behavior.

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Patch coverage

100.0% of changed lines covered (66/66)

File	Covered	Changed	Patch %
…/src/Fusion.Execution/Text/Json/SourceResultDocument.cs	55	55	100.0% 🟢
…/Fusion/src/Fusion.Execution/Text/Json/ThrowHelper.cs	6	6	100.0% 🟢
src/HotChocolate/Json/src/Json/JsonWriter.cs	5	5	100.0% 🟢

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Project coverage: 53.4% (227699/426465 lines)