fix: preserve Unicode characters in Pretty JSON formatting

[Copilot]

Purpose

Pretty JSON rendering was escaping non-ASCII characters (e.g., ÆØÅ) into \uXXXX, while raw JSON showed readable text. This change aligns formatter output with expected human-readable Unicode rendering.

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Scope

Select one primary concern:

• Bug fix (behavior change)
• Refactor (no behavior change)
• Documentation update
• Formatting / code cleanup
• Dependency / build update
• New feature

If this PR includes multiple unrelated concerns, please split it before requesting review.

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Description

Problem

Pretty JSON output used default serialization behavior in JsonFormatter.ToStringAsync, causing non-ASCII characters to be emitted as escaped Unicode sequences, reducing readability in JSON viewer pretty mode.

Solution

• Formatter serialization path
  • JsonFormatter now serializes using its configured _options instead of default JsonSerializer.Serialize(value).
• Unicode encoder configuration
  • Added JavaScriptEncoder.Create(UnicodeRanges.All) to formatter options to preserve readable Unicode text.
• Regression coverage
  • Added JsonFormatterTests.ToStringAsync_DoesNotEscapeUnicodeCharacters to assert ÆØÅ remains unescaped.

_options = new JsonSerializerOptions
{
    Encoder = JavaScriptEncoder.Create(UnicodeRanges.All)
};

var json = JsonSerializer.Serialize(value, _options);

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Verification

Steps:

1. Open JSON viewer content containing non-ASCII characters (e.g., {"name":"ÆØÅ"}).
2. Switch to Pretty view.
3. Confirm characters render as ÆØÅ (not \u00C6\u00D8\u00C5).

Expected outcome:
Pretty and Raw views both display readable Unicode characters for non-ASCII content.

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Screenshots / Recordings (if applicable)

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Commit Convention

We recommend using conventional commit prefixes:

• fix: – Bug fixes (behavior change)
• feat: – New features
• refactor: – Code changes without behavior change
• docs: – Documentation updates
• chore: – Maintenance, tooling, or dependency updates
• test: – Test additions or modifications

Clear commit messages make reviews easier and history more meaningful.

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Checklist

• The PR is focused on a single concern
• Commit messages follow the recommended convention
• Tests added or updated (if applicable)
• Documentation updated (if applicable)
• No unrelated cleanup included
• All tests pass

[greptile-apps]

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