Remote: match the old remote's hardware; old remote code in LEGACY

- LEGACY/remote/teensy/: old remote sketch from
  https://mangavalk.com/Hexapod/remote.git @ 492dece (reference only).
- remote/Config.h: sticks on A0-A5, Nextion on Serial1 (0/1), as in the
  old sketch; MPU6050 moved to Wire2 (25/24) since A4/A5 are Wire's pins.
- NextionUI: controls on a vscope-global "control" page added to the
  old HMI; keeps the old t1 status texts; the old page-1 b2 button (and
  serial 'U') enter Nextion upload passthrough, following the PC's baud.
- Docs: NEXTION.md, remote README wiring, CLAUDE.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-current/remote/README.md

@@ -11,17 +11,19 @@ at 100 Hz.
 From the repo root: `pio run -e remote`, flash with
 `pio run -e remote -t upload`, monitor with `pio device monitor -e remote`.
 
-## Wiring (placeholders; edit `Config.h` to match)
+## Wiring (from the old remote sketch in `LEGACY/remote/teensy/`; edit `Config.h` if yours differs)
 
 | Part | Signal | Teensy 4.1 pin |
 |------|--------|----------------|
 | nRF24L01 | MOSI / MISO / SCK | 11 / 12 / 13 (SPI0) |
 | nRF24L01 | CE / CSN | 9 / 10 |
 | nRF24L01 | VCC | 3.3 V, with a 10–100 µF cap right at the module |
-| MPU6050 | SDA / SCL | 18 / 19 (Wire) |
-| Nextion | TX → RX2, RX ← TX2 | 7 / 8 (Serial2), 5 V supply |
-| Left stick | X / Y / twist | A0 / A1 / A2 |
-| Right stick | X / Y / twist | A3 / A6 / A7 |
+| MPU6050 | SDA / SCL | **25 / 24 (Wire2)**: not 18/19, those are stick pins A4/A5 |
+| Nextion | TX → RX1, RX ← TX1 | 0 / 1 (Serial1), 5 V supply |
+| Sticks | 6 axes | A0–A5. Which axis is on which pin isn't known yet: reorder `STICK_PINS` until the `p` dump reads right |
+
+**MPU6050 rewiring:** the old remote had its MPU code switched off, probably
+because A4/A5 double as Wire's pins. Move the MPU's SDA/SCL to pins 25/24.
 
 Stick pots are wired 3.3 V – wiper – GND. **Never feed 5 V into a Teensy
 4.x analog pin.**
@@ -101,7 +103,7 @@ display attached.
 | `]` / `[` | height up / down 10% | | |
 | `c` | start / save calibration | `x` | cancel calibration |
 | `p` | print status (raw + mapped sticks, IMU, link, state, cal) | `d` | toggle 10 Hz packet dump |
-| `R` | reset stick cal to Config defaults | | |
+| `R` | reset stick cal to Config defaults | `U` | Nextion upload mode (USB ↔ display; power-cycle to leave) |
 
 ## Bench-check checklist