Improve test coverage

[v-volod]

What

This PR improves the error handling and test coverage for the design token conversion process. The converter now throws specific, descriptive errors for unsupported or malformed tokens instead of failing silently.

Why

This change makes the token conversion process more robust and easier to debug. Explicit errors clarify issues within the design token files, which was previously difficult with silent failures. The increased test coverage ensures the converter's reliability and prevents future regressions.

Changes

• Package.swift: Added new test resources to cover more file-related test cases.
• SnappThemingDesignTokensSupport:
  • Enhanced DesignTokensConverter to throw an error for malformed dynamic color groups.
  • Improved various DesignTokens...ValueExtractors to throw specific errors for unsupported types, unresolved references, and other invalid values.
  • Made several error enums public to be accessible for external consumers.
  • Simplified data conversion in SnappThemingParser+DesignTokens by removing a redundant check.
• SnappThemingDesignTokensSupportTests:
  • Significantly expanded SnappThemingDesignTokensParserTests with numerous new test cases for various failure scenarios (e.g., unsupported types, invalid values, malformed groups).
  • Added DesignTokensTokenValueExtractorTests to test type mismatch errors.
  • Introduced a PassthroughTokenProcessor utility to better isolate converter logic in tests.
  • Added new test resources (unknown, unsupported.extension) for file handling tests.
  • Enabled a previously disabled test.

[github-actions]

🛡️ Code Coverage Report

№	Target	Lines	Coverage
1	SnappThemingDesignTokensSupport	613	99.67%

Generated by Swift Coverage Action.