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/ServoDriver.h

@@ -3,7 +3,10 @@
 
 class ServoDriver {
 public:
-  void begin();                                       // attach all servos
-  void relaxAll();                                     // detach all servos - call when disarming
+  void begin();                                       // set up the PWM pins (no pulses yet)
+  void relaxAll();                                     // stop all pulses - call when disarming
   void writeLeg(int leg_index, const JointAngles& angles);
+
+  // Joint angle -> pulse through that servo's calibration (Config.h SERVOS).
+  static int degToMicros(int leg, int joint, float deg);
 };