Fixes external brightness resync after unplugging and reconnecting a USB-C dock.
Changes:
- Rebuilds the display map when DCP AV services are added or removed.
- Handles additional CoreGraphics display reconfiguration flags.
- Retries reconnect sync at 1s, 4s, and 8s so docks have time to expose the display path.
- Keeps brightness handling event-driven, with no polling watchdog.