Shape Python language runtime extension.

Provides a shape.language_runtime capability that embeds CPython for executing foreign "python" { ... } blocks in Shape programs.

ABI Exports

• shape_plugin_info() -- plugin metadata
• shape_abi_version() -- ABI version tag
• shape_capability_manifest() -- declares LanguageRuntime capability
• shape_capability_vtable(contract, len) -- generic vtable dispatch
• shape_language_runtime_vtable() -- direct vtable accessor