- Converted ChannelEventSink from JSM to ESM (.sys.mjs)
- Changed ChromeUtils.import() to ChromeUtils.importESModule() across all modules
- Updated .jsm file extensions to .sys.mjs for system module imports
- Replaced EXPORTED_SYMBOLS with export keyword in Helper.js, NetworkObserver.js, SimpleChannel.js, TargetRegistry.js, and JugglerFrameParent.jsm
- Updated EventEmitter import from resource://gre/modules/EventEmitter.jsm to .
- Created patch-upgrading-guide.md with step-by-step instructions for updating patches across Firefox versions
- Covers understanding patch system, preparation, general workflow, and common reject types
- Includes historical context patch merging section (no longer applicable after Firefox 146)
- Documents testing, validation, best practices, and complete example session
- Provides troubleshooting section for common issues and API changes
- Details