fix: add lid locating lip for flush fit

hardware/case/tripod-case-v3.scad

@@ -1,5 +1,5 @@
 // RemoteRig — Dual-ESP Tripod Case v3
-// v3c changes: screw-tightened tripod clamp + horizontal two-screw flat mounting plate interface.
+// v3d changes: screw-tightened tripod clamp + horizontal two-screw mount + flush locating-lip lid.
 // Coordinate system: all case/lid geometry uses bottom-origin Z.
 
 $fn = 36;
@@ -21,6 +21,12 @@ outer_d  = inner_d + wall*2 + tol*2;      // 32.8mm
 outer_h  = inner_h + wall*2;              // 19mm
 corner_r = 2.5;
 
+// Lid fit parameters
+lid_top_thick = 2.0;
+lid_lip_h     = 1.6;
+lid_clearance = 0.6;   // clearance around underside locating lip
+lid_lip_wall  = 1.2;   // thickness of perimeter lip/frame
+
 // Tripod clamp parameters
 pole_dia      = 35;       // nominal stand/pole diameter
 clamp_thick   = 4.0;      // ring wall thickness
@@ -133,18 +139,44 @@ module case_body() {
     }
 }
 
+module lid_locating_lip() {
+    // Thin underside frame that drops into the case opening. This registers the
+    // lid so it cannot skate/rock on the rim, while staying clear of screw posts.
+    lip_outer_w = inner_w + tol - lid_clearance;
+    lip_outer_d = inner_d + tol - lid_clearance;
+    lip_inner_w = lip_outer_w - lid_lip_wall*2;
+    lip_inner_d = lip_outer_d - lid_lip_wall*2;
+
+    translate([0, 0, -lid_lip_h])
+        difference() {
+            rounded_cube0(lip_outer_w, lip_outer_d, lid_lip_h, 1.0);
+            translate([0, 0, -0.1])
+                rounded_cube0(lip_inner_w, lip_inner_d, lid_lip_h + 0.2, 0.7);
+
+            // Corner reliefs so the lip doesn't interfere with screw posts.
+            for (x = [-1, 1], y = [-1, 1]) {
+                translate([x*(outer_w/2 - 5), y*(outer_d/2 - 5), lid_lip_h/2])
+                    cylinder(d=7.0, h=lid_lip_h + 0.4, center=true, $fn=24);
+            }
+        }
+}
+
 module case_lid() {
     difference() {
-        rounded_cube0(outer_w, outer_d, wall*2, 1.8);
+        union() {
+            // Thinner top cover; underside lip handles registration.
+            rounded_cube0(outer_w, outer_d, lid_top_thick, 0.8);
+            lid_locating_lip();
+        }
 
         for (x = [-1, 1], y = [-1, 1]) {
-            translate([x*(outer_w/2 - 5), y*(outer_d/2 - 5), -0.5])
-                cylinder(d=2.4, h=wall*2 + 1, center=false, $fn=20);
+            translate([x*(outer_w/2 - 5), y*(outer_d/2 - 5), -lid_lip_h - 0.5])
+                cylinder(d=2.4, h=lid_top_thick + lid_lip_h + 1, center=false, $fn=20);
         }
 
         for (x = [-outer_w/4, 0, outer_w/4]) {
-            translate([x, 0, wall*2/2])
-                cube([8, outer_d*0.6, wall*3], center=true);
+            translate([x, 0, lid_top_thick/2])
+                cube([8, outer_d*0.6, lid_top_thick*3], center=true);
         }
     }
 }
@@ -213,7 +245,7 @@ module tripod_clip() {
 
 module full_case() {
     case_body();
-    translate([0, 0, outer_h + 2]) case_lid();
+    translate([0, 0, outer_h]) case_lid();
     translate([0, outer_d/2 + pole_dia/2 + clamp_thick + 8, outer_h/2])
         rotate([90, 0, 0]) tripod_clamp();
 }