Security hardening, reliability, and performance improvements.
Security
- XPC helper now validates caller identity (UID-based defense-in-depth)
- AWDL state control uses atomic operations and returns accurate success/failure
- Sparkle update feed uses Info.plist as single source of truth
Reliability
- Fixed potential socket hang in network probes when fcntl fails
- Fixed potential pipe buffer deadlock in helper response test
- Complete App Group preferences reset on uninstall (prevents stale widget state)
- DiagnosticsExporter enforces background thread contract
Performance
- Game Mode detector caches app category lookups (eliminates repeated disk I/O)
- Dashboard gateway resolution moved off main thread
Quality
- Removed dead code (unused variables, redundant dispatch)
- Helper version synced with app version