refactor: consolidate JSON fallback logic in parseYamlSafely

[daniel-lxs]

Closes #5180
Closes #5139

Summary

Refactors the parseYamlSafely method to eliminate code duplication when handling JSON fallback for .roomodes files.

Changes

• Consolidated two separate JSON parsing blocks into a single flow
• Introduced needsJsonFallback variable for clearer logic
• Maintained proper error messages for different failure scenarios

Testing

• ✅ All tests passing (14 edge cases + 18 CustomModesManager tests)
• ✅ Linting and type checking pass

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Important

Refactor parseYamlSafely in CustomModesManager.ts to consolidate JSON fallback logic, improving clarity and reducing duplication.

• Refactor parseYamlSafely in CustomModesManager.ts:
  • Consolidates JSON fallback logic into a single flow, reducing code duplication.
  • Introduces needsJsonFallback variable for clearer logic.
  • Maintains distinct error messages for YAML and JSON parsing failures.
• Function Usage:
  • Updates calls to parseYamlSafely to include tryJsonFallback option in loadModesFromFile() and other relevant methods.
• Testing:
  • All tests pass, including 14 edge cases and 18 CustomModesManager tests.

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[delve-auditor]

✅ No security or compliance issues detected. Reviewed everything up to 77b0bda.

Security Overview

• 🔎 Scanned files: 1 changed file(s)

Detected Code Changes

Change Type	Relevant files
Refactor	► CustomModesManager.ts     Consolidate JSON fallback logic in parseYamlSafely method     Combine YAML error and non-object cases into single flow     Improve error handling for YAML/JSON parsing

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