尽快推进：收紧Python C API shim源码锚点

docs/linuxcnc-wasm-shims-source-map.md

@@ -55,6 +55,10 @@ only; it must not add CNC behavior and must not expand the temporary smoke parse
 
 - `core/wasm_shims/python_c_api_shim.cc` satisfies Python C API symbols used by
   LinuxCNC RS274/remap sources; it must not become Python execution.
+- The Python C API shim must return inert objects, null exceptions, false
+  callable/type checks, and successful module/type registration statuses only
+  to satisfy LinuxCNC `interp_python.cc`, `gcodemodule.cc`, and
+  `python_plugin.cc` link expectations; it must not call into CPython runtime.
 - `core/wasm_shims/pythonplugin/python_plugin.cc` must preserve LinuxCNC
   `PythonPlugin` status edges for `PLUGIN_NO_SECTION`, `PLUGIN_BAD_INIFILE`,
   `PLUGIN_PYTHON_NOT_INITIALIZED`, `PLUGIN_NO_CALLABLE`, and