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/Sticks.h

@@ -0,0 +1,47 @@
+#pragma once
+#include "Config.h"
+
+struct AxisCal {
+  int16_t min, center, max;   // raw ADC counts
+};
+
+// Processed stick values, -1000..1000 per logical axis (see StickAxis):
+// X + = right, Y + = forward, TWIST + = counterclockwise.
+struct StickFrame {
+  int16_t v[NUM_AXES] = {};
+  bool allCentered(int16_t tolerance) const;
+};
+
+class Sticks {
+public:
+  // Loads calibration from EEPROM (or Config defaults), then captures the
+  // resting center of each axis. Returns false if a stick looked deflected
+  // at power-on (center capture skipped for that axis).
+  bool begin();
+  void update();                               // read + filter + map all axes
+  const StickFrame& frame() const { return frame_; }
+  int16_t raw(int axis) const { return (int16_t)filtered_[axis]; }
+  const AxisCal& cal(int axis) const { return cal_[axis]; }
+
+  // Sweep calibration: start, move every stick to all its limits, release
+  // all sticks, then save. Output is held at zero while calibrating.
+  void startCalibration();
+  bool saveCalibration();                      // false = sweep too small, nothing saved
+  void cancelCalibration();
+  bool calibrating() const { return calibrating_; }
+  void resetCalibrationToDefaults();           // also clears EEPROM
+  void printCalibration(Stream& s) const;      // paste-able into Config.h
+
+private:
+  AxisCal cal_[NUM_AXES];
+  AxisCal sweep_[NUM_AXES];
+  float filtered_[NUM_AXES] = {};
+  StickFrame frame_;
+  bool calibrating_ = false;
+
+  int16_t readAveraged(int axis, int samples);
+  int16_t mapAxis(int axis, float raw) const;
+  void applyDefaults();
+  bool loadFromEeprom();
+  void saveToEeprom();
+};