feat: Preserve scalar styles and YAML tags when serializing YamlNode

[Tomas-Jakubec]

Summary

Fixes loss of scalar style and YAML tag information during round-trip serialization of YamlNodes. Resolves issue #749.

Problem

Currently YamlScalar does not retain the original scalar style, making it impossible to distinguish between:

• A plain numeric scalar (e.g. 123)
• A quoted string that looks like a number (e.g. "123")
  Additionally, YAML tags present in the parsed input were not emitted during serialization.

Root cause

• Scalar style (plain, single quoted, double quoted, literal, folded, JSON style) was not stored alongside the scalar value.
• Serialization of YamlNode relied on generic Kotlinx Serialization paths that discarded style and tag metadata.

Solution

• Introduced preservation of scalar style via an explicit enum (YamlNodeScalarStyle) mapped to SnakeYAML engine styles.
• Ensured YAML tags on nodes are carried through and emitted.
• Delegated encoding of YamlNode subclasses to YamlOutput, separating it from standard Kotlinx Serialization logic to avoid interference and to centralize style/tag handling.

Key changes

• Updated serialization pipeline to include style and tag emission.
• Adjusted YamlOutput to take responsibility for YamlNode encoding.
• Added/updated tests to assert round-trip fidelity for:
  • Quoted vs plain numeric-looking scalars
  • Block scalar styles (literal, folded)
  • Explicit tags

Backward compatibility

• Public API surface minimally affected (new enum exposed).
• Existing consumers not relying on style/tag round-tripping remain unaffected.
• No breaking rename/removal of existing types.

Performance

• Negligible impact; added metadata handling only during node serialization.

Risks / considerations

• Consumers constructing YamlScalar programmatically may now wish to specify a style explicitly. However, not specifying it results in original behavior.
• Ensure all new styles are covered in multiplatform targets. I tested all platforms except for tvosSimulatorArm64Test, please check.

Testing

• Added unit tests for style preservation and tag emission.
• Verified that previously failing scenario from issue YamlNodeSerializer corrupts data due to implicit types conversion #749 now passes.

Closes: #749

Let me know if a changelog entry format needs adjustment.

[Tomas-Jakubec]

Corrected the style using spotlessKotlinApply.

[Tomas-Jakubec]

@charleskorn

[Tomas-Jakubec]

@charleskorn can you review the PR please?

[Tomas-Jakubec]

@charleskorn please review the PR.