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/ko.json

@@ -760,6 +760,9 @@
   "cmd.joint_limits": "관절 제한",
   "cmd.joint_list": "관절 목록",
   "cmd.joint_motion_link": "모션 링크",
+  "cmd.joint_gear": "기어",
+  "cmd.joint_rack_pinion": "랙 앤 피니언",
+  "cmd.joint_screw": "나사",
   "cmd.joint_origin": "관절 원점",
   "cmd.joint_rigid_group": "강체 그룹",
   "cmd.joint_solve": "관절 해석",
@@ -1122,5 +1125,21 @@
   "Min": "최소",
   "Max": "최대",
   "Length": "길이",
-  "Area": "면적"
+  "Area": "면적",
+  "coupling.gear_1": "기어 1",
+  "coupling.gear_2": "기어 2",
+  "coupling.pinion": "피니언",
+  "coupling.rack": "랙",
+  "coupling.nut": "너트",
+  "coupling.radius_1": "반지름 1",
+  "coupling.radius_2": "반지름 2",
+  "coupling.internal": "내접 기어",
+  "coupling.pitch": "피치",
+  "coupling.picked": "선택됨",
+  "coupling.not_round": "원통 면이 아님",
+  "coupling.gear_1_pick": "기어 1 (선택 사항)",
+  "coupling.gear_2_pick": "기어 2 (선택 사항)",
+  "coupling.pinion_pick": "피니언 (선택 사항)",
+  "coupling.needs_turns": "회전하는 관절 두 개가 필요함",
+  "coupling.needs_turn_and_slide": "회전하는 관절과 미끄러지는 관절이 필요함"
 }