cap: keep z- wall untapered, taper only y± and z+ edges

cable_cap.scad

@@ -141,11 +141,10 @@ module cable_cap() {
     translate([case_w - CAP_ENGAGE + CAP_EXPLODE, -CAP_TOL - CAP_WALL, -CAP_TOL - CAP_WALL])
     difference() {
         // Outer shell: hull between two square profiles
-        //   X- (open end): inset to CAP_TIP wall thickness
-        //   X+ (closed end): full CAP_WALL thickness
+        //   z- wall is untapered (full CAP_WALL throughout); y±, z+ taper to CAP_TIP at open end
         hull() {
-            translate([0, CAP_WALL - CAP_TIP, CAP_WALL - CAP_TIP])
-                cube([0.01, _cap_bore_w + 2 * CAP_TIP, _cap_bore_h + 2 * CAP_TIP]);
+            translate([0, CAP_WALL - CAP_TIP, 0])
+                cube([0.01, _cap_bore_w + 2 * CAP_TIP, _cap_bore_h + CAP_WALL + CAP_TIP]);
 
             translate([CAP_ENGAGE + CAP_WALL - 0.01, 0, 0])
                 cube([0.01, _cap_bore_w + 2 * CAP_WALL, _cap_bore_h + 2 * CAP_WALL]);