Lock in Path A and hardware choice for Joy-Con ESP32 bridge

Path A (fully wireless: BT Classic host + BLE HID peripheral) is the
chosen architecture. Bridge will be self-powered off a LiPo in a
3D-printed case and sit next to the phone — no cables to the phone at
all. Hardware picked: ESP32-WROOM-32 USB-C dev board (original ESP32
silicon, has BT Classic, CP2102 onboard). Path B (USB-CDC serial) kept
in the doc as a fallback if dual-mode BT coexistence proves painful
during bring-up.

docs/joycon-esp32-bridge.md

@@ -1,8 +1,29 @@
 # Joy-Con ESP32 Bridge — Design Notes
 
-Design sketch for replacing the 8BitDo USB Wireless Adapter 2 with a DIY
+Design for replacing the 8BitDo USB Wireless Adapter 2 with a DIY
 ESP32-based Joy-Con bridge. Not yet implemented — this doc captures the
-plan so it's ready to pick up later.
+plan so it's ready to pick up when the hardware arrives.
+
+## Decisions
+
+- **Chosen architecture: Path A (fully wireless).** The bridge pairs with
+  the Joy-Con over BT Classic, then re-advertises itself to the phone as
+  a BLE HID gamepad. No cable between the phone and the bridge. The
+  bridge runs off its own battery (LiPo + charging circuit, or a small
+  USB power bank).
+- **Chosen hardware: ESP32-WROOM-32 USB-C dev board**
+  ([Amazon.ca link](https://www.amazon.ca/ESP-WROOM-32-NodeMCU-Bluetooth-Development-Microcontroller/dp/B0CHBMFJBQ)).
+  Original ESP32 silicon (BT Classic + BLE, dual-mode radio), CP2102
+  USB-serial for programming, USB-C for power + flashing.
+- **Form factor plan:** 3D-printed case housing the ESP32 + a LiPo
+  battery + a small TP4056-style USB-C charge/protection board. Sits on
+  the couch next to the phone, pairs with the Joy-Con, connects to the
+  phone wirelessly.
+- **Path B (USB serial) is the fallback.** If the dual-mode BT
+  coexistence on the ESP32 turns out to be too painful, we can fall back
+  to sending button state over the on-board CP2102's USB serial —
+  everything on the Joy-Con side is identical, and the app-side changes
+  for a USB-CDC reader are documented below.
 
 ## Why