Add G20 left-hand MuJoCo PLAN bridge, assets, and docs.

Bring in kinematic hard-write control with mesh-convex collision projection, SDK mapping aligned to Isaac, launch/run scripts, and implementation/tech writeups.

run_g20_mujoco_plan.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# MuJoCo G20 左手仿真桥
+# 默认订阅 /g20/cb_left_hand_control_cmd（0~255）
+# 发布 /sim/mujoco/g20/left/joint_state
+# 默认 1.35× 墙钟 + 关节限速；可用 --speed / --slew-rad-s 再调
+set -eo pipefail
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$ROOT"
+
+set +u
+# shellcheck disable=SC1091
+source /opt/ros/jazzy/setup.bash
+if [[ -f "$ROOT/install/setup.bash" ]]; then
+  # shellcheck disable=SC1091
+  source "$ROOT/install/setup.bash"
+fi
+set -u
+
+VENV_SITE="$ROOT/venv/lib/python3.12/site-packages"
+if [[ -d "$VENV_SITE" ]]; then
+  export PYTHONPATH="$VENV_SITE${PYTHONPATH:+:$PYTHONPATH}"
+fi
+
+# 源码优先（含 urdf 资产）
+PKG_SRC="$ROOT/src/linkerhand-sim/linker_hand_mujoco_ros2"
+export PYTHONPATH="$PKG_SRC${PYTHONPATH:+:$PYTHONPATH}"
+
+exec python3 -m linker_hand_mujoco_ros2.g20_plan_bridge "$@"