Joints: gears, rack and pinion, and screws (#1524)

Motion links can carry a coupling (gear pair, rack and pinion, screw) whose ratio follows radii, picked round faces or pitch. Design format 23.

Co-authored-by: SychPL <SychPL@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

assets/locales/en.json

@@ -125,6 +125,9 @@
   "cmd.joint_limits": "Joint Limits",
   "cmd.joint_list": "List Joints",
   "cmd.joint_motion_link": "Motion Link",
+  "cmd.joint_gear": "Gear",
+  "cmd.joint_rack_pinion": "Rack and Pinion",
+  "cmd.joint_screw": "Screw",
   "cmd.joint_origin": "Joint Origin",
   "cmd.joint_rigid_group": "Rigid Group",
   "cmd.joint_solve": "Solve Joints",
@@ -1377,5 +1380,21 @@
   "Centre to centre": "Centre to centre",
   "Overall length": "Overall length",
   "Min": "Min",
-  "Max": "Max"
+  "Max": "Max",
+  "coupling.gear_1": "Gear 1",
+  "coupling.gear_2": "Gear 2",
+  "coupling.pinion": "Pinion",
+  "coupling.rack": "Rack",
+  "coupling.nut": "Nut",
+  "coupling.radius_1": "Radius 1",
+  "coupling.radius_2": "Radius 2",
+  "coupling.internal": "Internal gear",
+  "coupling.pitch": "Pitch",
+  "coupling.picked": "picked",
+  "coupling.not_round": "not a round face",
+  "coupling.gear_1_pick": "Gear 1 (optional)",
+  "coupling.gear_2_pick": "Gear 2 (optional)",
+  "coupling.pinion_pick": "Pinion (optional)",
+  "coupling.needs_turns": "needs two joints that turn",
+  "coupling.needs_turn_and_slide": "needs a joint that turns and one that slides"
 }