Initial import: robot firmware + PlatformIO two-env scaffold

Robot-side firmware (Teensy 4.0) imported unchanged as extracted.
platformio.ini defines [env:robot] (teensy40) and [env:remote]
(teensy41); scripts/select_src_dir.py points each env at its own
sketch folder so robot/ and remote/ stay Arduino-style sketches.

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

2026-current/platformio.ini

@@ -0,0 +1,29 @@
+; Hexapod: two firmware images in one project.
+;   pio run -e robot            build robot/  (Teensy 4.0)
+;   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
+;
+; shared/ is the library directory. Both sketches #include <HexapodProtocol.h>
+; from shared/HexapodProtocol/, which is the single definition of the wire
+; protocol (CmdPacket, FLAG_* bits, radio address/channel/rate/PA/payload size).
+
+[platformio]
+default_envs = robot, remote
+lib_dir = shared
+
+[env]
+platform = teensy
+framework = arduino
+monitor_speed = 115200
+extra_scripts = pre:scripts/select_src_dir.py
+lib_deps =
+    nrf24/RF24@^1.4.9
+
+[env:robot]
+board = teensy40
+custom_src_dir = robot
+
+[env:remote]
+board = teensy41
+custom_src_dir = remote