Fix #5180: Handle empty .roomodes files gracefully

[roomote]

Fixes #5180 - Mode selector missing after update due to empty .roomodes files causing schema validation errors.

Enhanced CustomModesManager to handle empty/malformed .roomodes files gracefully by detecting empty files and initializing them with proper structure, preventing 'customModes: Required' errors.

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Important

Enhances CustomModesManager to handle empty or malformed .roomodes files by initializing them with default content and improving error handling.

• Behavior:
  • CustomModesManager now handles empty .roomodes files by initializing them with a default structure using createDefaultRoomodesContent().
  • Enhances parseYamlSafely() to return an empty object for empty or whitespace-only content and handle null results from YAML parser.
  • Attempts to fix malformed .roomodes files by writing default content if schema validation fails due to customModes type issues.
• Functions:
  • Adds createDefaultRoomodesContent() to generate default YAML content for .roomodes files.
  • Modifies loadModesFromFile() to initialize empty .roomodes files with default content.
  • Updates getCustomModesFilePath() and resetCustomModes() to use createDefaultRoomodesContent().
• Logging:
  • Adds logging for empty content detection and attempts to fix malformed files in CustomModesManager.

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[delve-auditor]

✅ No security or compliance issues detected. Reviewed everything up to 08adc06.

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