fix: use upstream dongle firmware

Use the common xow_dongle.bin image from the upstream driver for the
GUI session instead of selecting the older 02E6-specific image. Update
the firmware download script and plan to document the same upstream flow.
Keep the extended RX diagnostics used to inspect controller discovery.

Co-Authored-By: openai/gpt-5.6-luna: traced firmware and pairing behavior

PLAN.md

@@ -40,7 +40,7 @@ User-space macOS app that speaks to the Xbox Wireless Dongle (MT76xx chip) and e
 - Phase 1 (GIP + auth): ported and unit-tested.
 - Phase 2 (USB transport): probe/open, async read pump, vendor requests,
   bulk write. Verified on hardware.
-- Phase 3 (MT76 chip): register/EFUSE access, firmware load (per-PID images),
+- Phase 3 (MT76 chip): register/EFUSE access, firmware load,
   radio init (registers, crystal, MAC/BSSID, channel eval, beacon). Verified
   end-to-end: `radio-init` completes, beacon TX enabled, FCE shows firmware
   running.
@@ -282,12 +282,9 @@ on first packet, so a fresh adapter yields its single client on demand.
 
 Firmware binaries are downloaded from Microsoft Windows Update driver catalog:
 
-| PID  | Dongle Type            | Firmware File        |
-| ---- | ---------------------- | -------------------- |
-| 02E6 | Old dongle             | xone_dongle_02e6.bin |
-| 02FE | New dongle             | xone_dongle_02fe.bin |
-| 02F9 | Built-in (ASUS/Lenovo) | xone_dongle_02f9.bin |
-| 091E | Surface Book 2         | xone_dongle_091e.bin |
+| PID  | Dongle Type            | Firmware File |
+| ---- | ---------------------- | ------------- |
+| all  | Supported dongles     | xow_dongle.bin |
 
 Downloaded via `scripts/download-firmware.sh` (port of `install/firmware.sh`).