Each pybind extension module holds its own copy of the ImGui/ImPlot globals (extension modules are loaded RTLD_LOCAL), so the viewer that owns the contexts must share the pointers explicitly. Without this, client plotting GUIs and user plotting scripts (e.g. the implot sample) crash on null context pointers.
PiperOrigin-RevId: 951917287
Change-Id: I639a173c2ae9f1af4feaf57aff7b5c81854b7393
Following the export declarations in Dear ImGui and ImPlot METADATA, this change updates MuJoCo's Copybara configuration (copy.bara.sky) to export and transform the Python bindings. `//third_party/dear_imgui/google/py` exports to `python/mujoco/experimental/dear_imgui` and `//third_party/implot/google/py` exports to `python/mujoco/experimental/implot`.
PiperOrigin-RevId: 925293624
Change-Id: Ie6e32d247a6f7fc24bb36ae7060f2075d8efeb26