Draft: shared protocol, remote firmware, project docs

Not yet verified on hardware.

- shared/HexapodProtocol: CmdPacket (now 20 bytes, adds remote_roll /
  remote_pitch), FLAG_* bits and radio settings as the single protocol
  definition; static payload size = sizeof(CmdPacket) on both radios.
- robot: use the shared protocol; vx = forward (harness w/x <-> q/e);
  InputMapper adds remote tilt on top of the right stick when
  FLAG_REMOTE_GYRO is set, and robot.ino no longer zeroes stick
  roll/pitch when it's off.
- remote (Teensy 4.1): Sticks (calibration, EEPROM), RemoteIMU,
  RemoteState (interlocks, link-loss disarm, smoothing), PacketBuilder,
  RadioLink, NextionUI, SerialConsole.
- CLAUDE.md, README.md, remote/README.md, remote/NEXTION.md.

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

2026-current/remote/SerialConsole.h

@@ -0,0 +1,14 @@
+#pragma once
+#include "UiTypes.h"
+
+// USB serial console (115200). Mirrors every touchscreen control with a
+// single keystroke, so the remote can be bench-tested with no Nextion
+// attached, plus a few diagnostics. Key map in remote/README.md.
+class SerialConsole {
+public:
+  enum class Local : uint8_t { None, PrintStatus, ToggleDump, ResetCal };
+
+  // Returns true with either `ui` set (a normal operator command) or
+  // `local` set (a console-only diagnostic the sketch handles itself).
+  bool poll(UiEvent& ui, Local& local);
+};