Polish green context API: docs, error handling, simplification

- dev.create_context raises ValueError (not NotImplementedError) when
  options or resources are missing.
- Cache version checks (_check_green_ctx_support, _check_workqueue_support)
  at module level; raise ValueError instead of NotImplementedError.
- Simplify _device_resources.pyx: merge _as_uint and _count_to_sm_count
  into _to_sm_count; inline unsigned int casts for coscheduled params.
- Add green context classes to api.rst (Context, ContextOptions,
  DeviceResources, SMResource, SMResourceOptions, WorkqueueResource,
  WorkqueueResourceOptions).
- Update all docstrings to NumPy style with Attributes/Parameters/Returns
  sections matching the existing codebase convention.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: leofang

cuda_core/cuda/core/_context.pyx

@@ -149,7 +149,7 @@ cdef class ContextOptions:
 
     Attributes
     ----------
-    resources : :obj:`~_context.DeviceResourcesT`
+    resources : :obj:`~cuda.core.typing.DeviceResourcesT`
         Device resources used to create a green context.
     """
     resources: DeviceResourcesT

cuda_core/cuda/core/_device.pyx

@@ -1302,11 +1302,15 @@ class Device:
         cdef GreenCtxHandle h_green
 
         if options is None:
-            raise NotImplementedError("WIP: https://github.com/NVIDIA/cuda-python/issues/189")
+            raise ValueError(
+                "options with device resources must be provided to create a green context"
+            )
 
         options = check_or_create_options(ContextOptions, options, "Context options")
         if options.resources is None:
-            raise NotImplementedError("WIP: https://github.com/NVIDIA/cuda-python/issues/189")
+            raise ValueError(
+                "ContextOptions.resources must be provided to create a green context"
+            )
 
         resources = tuple(options.resources)
         if len(resources) == 0:
@@ -1334,9 +1338,9 @@ class Device:
 
             h_green = create_green_ctx_handle(
                 c_resources,
-                <unsigned int>n_resources,
-                <cydriver.CUdevice>self._device_id,
-                <unsigned int>cydriver.CUgreenCtxCreate_flags.CU_GREEN_CTX_DEFAULT_STREAM,
+                <unsigned int>(n_resources),
+                <cydriver.CUdevice>(self._device_id),
+                <unsigned int>(cydriver.CUgreenCtxCreate_flags.CU_GREEN_CTX_DEFAULT_STREAM),
             )
             if h_green.get() == NULL:
                 HANDLE_RETURN(get_last_error())