- Updated plugin extension discovery test to use XDG_DATA_HOME instead of HOME for environment isolation.
- Replaced manual path construction with getPluginsDir() utility for consistency.
- Added XDG directory structure setup and path cache rebuild to ensure correct plugin resolution.
- Added `toExtensionId()` method to all capability types for granular extension identification and disabling.
- Added `disabledExtensions` and `includeDisabled` options to LoadOptions for filtering disabled capabilities by extension ID.
- Added plugin manifest support for `extensions` entry points with automatic discovery from installed plugins.
- Fixed skill loading to properly respect disabled skill names from custom directories.
- Improved cross-platform path handling by using `path.basename()` instead of string splitting in context file and state manager.
- Refactored capability index loading to validate source metadata and filter disabled extensions before processing.
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