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/RemoteState.h

@@ -0,0 +1,59 @@
+#pragma once
+#include "UiTypes.h"
+#include "Sticks.h"
+#include "RemoteIMU.h"
+#include "SmoothedValue.h"
+#include "Config.h"
+
+// Operator-facing state of the remote: every toggle the touchscreen can
+// flip, the interlocks around them, and the smoothed setpoints. It does not
+// know the wire format - PacketBuilder turns this into a CmdPacket.
+class RemoteState {
+public:
+  void begin();
+
+  // Applies one operator request. Sticks are needed for the arm interlock
+  // and calibration, the IMU for re-zeroing. Returns true if accepted;
+  // rejections leave an explanation in message().
+  bool handle(const UiEvent& e, Sticks& sticks, RemoteIMU& imu, uint32_t now_ms);
+
+  // Advances smoothers and link-loss handling. Call once per TX tick.
+  void update(float dt, bool link_ok, uint32_t now_ms);
+
+  bool armed() const        { return armed_; }
+  bool standRequested() const { return stand_; }
+  bool gaitWave() const     { return gait_wave_; }
+  bool modeB() const        { return mode_b_; }
+  bool rstickXlate() const  { return rstick_xlate_; }
+  bool remoteGyro() const   { return remote_gyro_; }
+  bool robotGyro() const    { return robot_gyro_; }
+
+  uint8_t speedTarget() const  { return speed_target_; }
+  uint8_t speedCurrent() const { return (uint8_t)lroundf(speed_.current); }
+  float remoteTiltBlend() const { return tilt_blend_.current; }   // 0..1, fades on the gyro toggle
+
+  const char* message(uint32_t now_ms) const { return now_ms < message_until_ms_ ? message_ : ""; }
+  void setMessage(const char* msg, uint32_t now_ms);
+
+  void fillView(UiView& v, uint32_t now_ms) const;
+
+private:
+  bool armed_ = false;
+  bool stand_ = false;
+  bool gait_wave_ = false;
+  bool mode_b_ = false;
+  bool rstick_xlate_ = false;
+  bool remote_gyro_ = false;
+  bool robot_gyro_ = false;
+  bool calibrating_ = false;
+
+  uint8_t speed_target_ = SPEED_SCALE_DEFAULT;
+  SmoothedValue speed_{SPEED_SCALE_RATE_PER_SEC};
+  SmoothedValue tilt_blend_{REMOTE_TILT_FADE_PER_SEC};
+
+  bool link_was_ok_ = false;
+  const char* message_ = "";
+  uint32_t message_until_ms_ = 0;
+
+  void disarm();
+};