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/robot/Limits.h

@@ -0,0 +1,15 @@
+#pragma once
+#include "Kinematics.h"
+
+class Limits {
+public:
+  // Clamps a foot target into a conservative safe envelope around the leg's neutral stance.
+  static FootTarget clampWorkspace(int leg_index, const FootTarget& target);
+
+  // Rate-limits a joint angle change to the servo's real max speed.
+  static float clampJointRate(float current_deg, float target_deg, float max_deg_per_sec, float dt);
+
+  // Coarse safety check: are enough legs grounded right now to be stable.
+  // A real support-polygon/center-of-mass check is a good later upgrade.
+  static bool stancePolygonOk(const bool in_stance[6]);
+};