Fix schema settings serialization during export

[tobias-tengler]

No description provided.

[Copilot]

Pull request overview

This PR fixes the JSON serialization behavior of the schema *-settings.json file during schema export, ensuring certain characters (e.g., </>) are preserved in their unescaped form when rewriting an existing settings file.

Changes:

• Introduce shared JsonWriterOptions for settings file writing with JavaScriptEncoder.UnsafeRelaxedJsonEscaping.
• Use the shared writer options in both “update existing settings file” and “create new settings file” code paths.
• Add a regression test ensuring angle brackets remain unescaped after updating an existing settings file.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/HotChocolate/Core/src/Types/Execution/Internal/SchemaFileExporter.cs	Reuses a shared Utf8JsonWriter configuration to preserve unescaped characters when writing settings JSON.
src/HotChocolate/AspNetCore/test/AspNetCore.CommandLine.Tests/SchemaExportCommandTests.cs	Adds a regression test verifying angle brackets are preserved when an existing settings file is updated.

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