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/zh.json

@@ -125,6 +125,9 @@
   "cmd.joint_limits": "接头限制",
   "cmd.joint_list": "列出接头",
   "cmd.joint_motion_link": "运动关联",
+  "cmd.joint_gear": "齿轮",
+  "cmd.joint_rack_pinion": "齿轮齿条",
+  "cmd.joint_screw": "螺旋",
   "cmd.joint_origin": "接头原点",
   "cmd.joint_rigid_group": "刚性组",
   "cmd.joint_solve": "解算接头",
@@ -1377,5 +1380,21 @@
   "Centre to centre": "中心距",
   "Overall length": "总长",
   "Min": "最小",
-  "Max": "最大"
+  "Max": "最大",
+  "coupling.gear_1": "齿轮 1",
+  "coupling.gear_2": "齿轮 2",
+  "coupling.pinion": "小齿轮",
+  "coupling.rack": "齿条",
+  "coupling.nut": "螺母",
+  "coupling.radius_1": "半径 1",
+  "coupling.radius_2": "半径 2",
+  "coupling.internal": "内齿轮",
+  "coupling.pitch": "螺距",
+  "coupling.picked": "已拾取",
+  "coupling.not_round": "不是圆柱面",
+  "coupling.gear_1_pick": "齿轮 1（可选）",
+  "coupling.gear_2_pick": "齿轮 2（可选）",
+  "coupling.pinion_pick": "小齿轮（可选）",
+  "coupling.needs_turns": "需要两个旋转接头",
+  "coupling.needs_turn_and_slide": "需要一个旋转接头和一个滑动接头"
 }