fix: improve YAML parsing for custom modes to be more lenient

[roomote]

Summary

This PR fixes issue #7138 where custom modes would disappear or fail to load due to overly strict YAML parsing and validation.

Problem

Users were experiencing:

• Custom modes disappearing after minor edits
• YAML parsing being too strict and failing on minor syntax issues
• .roomodes files not accepting JSON format as fallback
• Unhelpful error messages when YAML parsing failed

Solution

Implemented a multi-layered approach to make custom mode loading more robust:

1. Lenient YAML Parsing

• Added strict: false and uniqueKeys: false options to YAML parser
• Allows duplicate keys (last one wins) and other minor issues

2. Multiple Fallback Strategies

For .roomodes files, implemented fallback chain:

1. Try parsing as YAML with lenient options
2. Try parsing as JSON (for backward compatibility)
3. Try parsing original content without preprocessing
4. Attempt to extract partial modes from corrupted YAML
5. Return empty array with helpful error message if all fail

3. Mode Recovery Mechanisms

• Automatically fix common issues before validation (trim whitespace, fix groups format)
• Provide default values for missing required fields
• Recover modes with minimal required fields (slug) by generating sensible defaults
• Filter out invalid group names while preserving valid ones

4. Better Error Handling

• More helpful error messages with specific suggestions
• Warning messages for partially invalid modes (load what's valid)
• Preserve complex group syntax with fileRegex

Testing

• Added comprehensive test suite for lenient parsing scenarios
• Tests for JSON fallback, partial recovery, missing fields, invalid groups
• All existing tests pass
• New tests cover edge cases and recovery mechanisms

Impact

Users should now experience:

• More resilient custom mode loading
• Better recovery from syntax errors
• Helpful error messages when issues occur
• No more disappearing modes after minor edits

Fixes #7138

---

Important

Improves YAML parsing for custom modes with lenient parsing, fallback strategies, and comprehensive testing.

• Behavior:
  • parseYamlSafely() in CustomModesManager.ts now uses lenient YAML parsing with strict: false and uniqueKeys: false.
  • Implements fallback strategies for .roomodes files: JSON parsing, original content parsing, partial mode extraction.
  • Adds recovery mechanisms for modes with missing fields or invalid groups.
  • Provides more helpful error messages and warnings for invalid modes.
• Testing:
  • Adds CustomModesManager.lenientParsing.spec.ts to test lenient parsing, JSON fallback, and recovery mechanisms.
  • Adds CustomModesManager.yamlEdgeCases.spec.ts to test edge cases like BOM handling, invisible characters, and complex structures.
• Misc:
  • Updates loadModesFromFile() to handle single mode objects and invalid arrays.
  • Enhances fixCommonModeIssues() and recoverInvalidMode() for better mode validation and recovery.

^{This description was created by for 7bda2dc. You can customize this summary. It will automatically update as commits are pushed.}

[roomote]

Reviewing my own code is like debugging in a mirror - everything looks backwards but the bugs are still mine.

[roomote]

The extractPartialModes() method iterates through every line of potentially large YAML files. For very large corrupted files, this could cause performance issues. Consider adding a size limit or line count limit (e.g., max 10,000 lines) to prevent hanging on massive files.

[roomote]

For consistency, consider using the logger utility (already imported at line 14) instead of console.log:

Suggested change

	console.log(`[CustomModesManager] Successfully parsed ${filePath} as JSON`)
	logger.info(`[CustomModesManager] Successfully parsed ${filePath} as JSON`)

[roomote]

Similarly here, consider using logger.info for consistency:

Suggested change

	console.log(`[CustomModesManager] Successfully parsed ${filePath} with original content`)
	logger.info(`[CustomModesManager] Successfully parsed ${filePath} with original content`)

[roomote]

And here as well:

Suggested change

	console.log(
	logger.info(
	`[CustomModesManager] Extracted ${partialModes.customModes.length} modes from partially corrupted YAML`,
	)

[roomote]

After logging the error, should we return null immediately instead of continuing? The current approach might mask other issues:

Suggested change

	console.error("[CustomModesManager] Failed to extract partial modes:", error)
	logger.error("[CustomModesManager] Failed to extract partial modes:", error)
	return null