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.cpp

@@ -0,0 +1,30 @@
+#include "SerialConsole.h"
+#include <Arduino.h>
+
+bool SerialConsole::poll(UiEvent& ui, Local& local) {
+  ui = UiEvent{};
+  local = Local::None;
+  while (Serial.available()) {
+    char c = Serial.read();
+    switch (c) {
+      case 'a': ui.cmd = UiCmd::ToggleArm;         return true;
+      case 'k': ui.cmd = UiCmd::Disarm;            return true;
+      case 's': ui.cmd = UiCmd::ToggleStand;       return true;
+      case 'g': ui.cmd = UiCmd::ToggleGait;        return true;
+      case 'm': ui.cmd = UiCmd::ToggleWalkMode;    return true;
+      case 't': ui.cmd = UiCmd::ToggleRStickXlate; return true;
+      case 'r': ui.cmd = UiCmd::ToggleRemoteGyro;  return true;
+      case 'b': ui.cmd = UiCmd::ToggleRobotGyro;   return true;
+      case '+': case '=': ui.cmd = UiCmd::SpeedUp;   return true;
+      case '-': case '_': ui.cmd = UiCmd::SpeedDown; return true;
+      case 'z': ui.cmd = UiCmd::ZeroGyro;          return true;
+      case 'c': ui.cmd = UiCmd::CalStartSave;      return true;
+      case 'x': ui.cmd = UiCmd::CalCancel;         return true;
+      case 'p': local = Local::PrintStatus;        return true;
+      case 'd': local = Local::ToggleDump;         return true;
+      case 'R': local = Local::ResetCal;           return true;
+      default: break;   // ignore line endings and unknown keys
+    }
+  }
+  return false;
+}