Robot: Teensy 3.6 with the old robot's servo wiring and calibration

- LEGACY/Hexapod_Teensy/: old robot sketch (reference only).
- platformio.ini: robot env targets teensy36 (owner-confirmed board).
- Config.h: per-servo SERVOS table (pin, pulse at 0 deg, signed
  us/deg, pulse limits) built from the old sketch's pins, ranges, trims
  and the old Unity servo directions. Rear-left/front-left coxa offsets
  set to 0: the owner re-horns those two servos (the old +-90 left them
  at the end of travel; the sim showed them clamping).
- ServoDriver: 18 servos on hardware PWM (50 Hz, 16-bit); the Teensy 3.6
  Servo library stops at 12.
- Radio on CE 39 / CSN 15 with SPI SCK on pin 14.
- sim: analogWrite/PWM shims, pulses decoded through SERVOS (API v6).
- Docs: CLAUDE.md, READMEs.

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

2026-current/robot/Comms.cpp

@@ -9,6 +9,7 @@ static_assert(HXP_RADIO_DATA_RATE == RF24_250KBPS && HXP_RADIO_PA_LEVEL == RF24_
 static RF24 radio(RADIO_CE_PIN, RADIO_CSN_PIN);
 
 bool Comms::begin() {
+  SPI.setSCK(RADIO_SCK_PIN);   // alternate SCK pin (see Config.h); before RF24 starts SPI
   radio_present_ = radio.begin();
   if (radio_present_) {
     radio.setPayloadSize(HXP_RADIO_PAYLOAD);   // mismatched protocol versions won't be received at all