2026: OpenSCAD robot and remote, physical joint limits, model in Unity

hardware/openscad/ rebuilds the broken Fusion models as OpenSCAD:
body (top/bottom plate, standoffs, battery bay, switch), legs (coxa
bracket, femur link, tibia, horn adapters, TPU socks, servo cables),
the whole robot, and the remote (shell, lid, Nextion 3.5", JH-D400X-R4
sticks, 18650 UPS board, IMU, Teensy 4.0, USB-C breakout). Every part
was checked by slicing against the original STEP solids; the original's
bugs are fixed and listed in PLANNING.md.

The robot now uses a hexagon leg layout (corner legs 60 deg round from
the mid legs; the corner coxa brackets need turning on their splines).
Physical limits from a collision sweep of the model are in Config.h:
per-leg coxa limits and LEG_CLEARANCE_MM 56 (a leg is 55.2 mm wide at
the joints); the sim API exports them (version 7). sim_smoke passes.

Unity loads the model (export_unity.py -> Resources/OpenScadModel,
OpenScadModel.cs builds a new rig in place of the old scene's robot).
The PCB model's mounting holes now use the exact EasyEDA grid. README
shows renders of both.

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

2026-current/sim/HexapodSimApi.cpp

@@ -40,13 +40,14 @@ HXSIM_API void hxsim_get_geometry(HxGeometry* g) {
     g->mount_x_mm[i] = LEG_MOUNT_X_MM[i];
     g->mount_y_mm[i] = LEG_MOUNT_Y_MM[i];
     g->mount_angle_deg[i] = LEG_MOUNT_ANGLE_DEG[i];
+    g->coxa_min_deg[i] = COXA_MIN_DEG[i];
+    g->coxa_max_deg[i] = COXA_MAX_DEG[i];
   }
   g->coxa_mm = COXA_LEN_MM;
   g->femur_mm = FEMUR_LEN_MM;
   g->tibia_mm = TIBIA_LEN_MM;
   g->stance_radius_mm = STANCE_RADIUS_MM;
   g->stance_height_mm = STANCE_HEIGHT_MM;
-  g->coxa_min_deg = COXA_MIN_DEG;   g->coxa_max_deg = COXA_MAX_DEG;
   g->femur_min_deg = FEMUR_MIN_DEG; g->femur_max_deg = FEMUR_MAX_DEG;
   g->tibia_min_deg = TIBIA_MIN_DEG; g->tibia_max_deg = TIBIA_MAX_DEG;
   g->control_hz = CONTROL_HZ;

2026-current/sim/HexapodSimApi.h

@@ -18,7 +18,7 @@
 #endif
 
 // Bump whenever a signature or struct below changes; the C# side checks it.
-#define HXSIM_API_VERSION 6
+#define HXSIM_API_VERSION 7
 
 #define HXSIM_NUM_LEGS 6
 
@@ -30,7 +30,8 @@ typedef struct {
   float mount_angle_deg[HXSIM_NUM_LEGS];
   float coxa_mm, femur_mm, tibia_mm;
   float stance_radius_mm, stance_height_mm;
-  float coxa_min_deg, coxa_max_deg;
+  float coxa_min_deg[HXSIM_NUM_LEGS];   // per leg: corner legs can't swing far towards the mid leg
+  float coxa_max_deg[HXSIM_NUM_LEGS];
   float femur_min_deg, femur_max_deg;
   float tibia_min_deg, tibia_max_deg;
   float control_hz;