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/robot/Comms.h

@@ -1,26 +1,6 @@
 #pragma once
 #include <Arduino.h>
-
-// Remote -> robot, sent at a fixed rate. Kept as the single source of truth
-// here so a future remote sketch just has to fill this same struct and
-// radio.write() it - nothing on the robot side needs to change.
-struct CmdPacket {
-  int16_t vx = 0, vy = 0;           // left stick: strafe / forward-back, -1000..1000
-  int16_t yaw_rate = 0;             // left stick twist, -1000..1000
-  int16_t rx = 0, ry = 0, rz = 0;   // right stick: roll/pitch/yaw OR X/Y/height, per flags
-  uint8_t speed_scale = 128;        // 0-255
-  uint8_t flags = 0;                // bit-packed, see FLAG_* below
-  uint8_t seq = 0;
-};
-
-constexpr uint8_t FLAG_ARMED        = 1 << 0;
-constexpr uint8_t FLAG_STAND        = 1 << 1;   // 0 = sit requested, 1 = stand requested
-constexpr uint8_t FLAG_WALK         = 1 << 2;   // stick past deadzone -> walking
-constexpr uint8_t FLAG_MODE_B       = 1 << 3;   // 0 = mode A direct, 1 = mode B heading-hold
-constexpr uint8_t FLAG_RSTICK_XLATE = 1 << 4;   // 0 = right stick = rotation, 1 = translation
-constexpr uint8_t FLAG_GAIT_WAVE    = 1 << 5;   // 0 = tripod requested, 1 = wave requested
-constexpr uint8_t FLAG_REMOTE_GYRO  = 1 << 6;   // remote tilt feedforward enabled
-constexpr uint8_t FLAG_ROBOT_GYRO   = 1 << 7;   // robot stabilization feedback enabled
+#include <HexapodProtocol.h>   // CmdPacket + FLAG_* + radio settings, shared with the remote (shared/)
 
 class Comms {
 public: