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/platformio.ini

@@ -1,5 +1,5 @@
 ; Hexapod: two firmware images in one project.
-;   pio run -e robot            build robot/  (Teensy 4.0)
+;   pio run -e robot            build robot/  (Teensy 3.6)
 ;   pio run -e remote           build remote/ (Teensy 4.1)
 ;   pio run -e robot -t upload  flash (Teensy Loader / teensy_cli)
 ;   pio device monitor -e robot serial monitor at 115200
@@ -21,7 +21,7 @@ lib_deps =
     nrf24/RF24@^1.4.9
 
 [env:robot]
-board = teensy40
+board = teensy36
 custom_src_dir = robot
 
 [env:remote]