Inconsistent lifetime management across `from_handle` / `from_*` APIs

Summary

Audit of all public from_handle / from_* methods in cuda.core reveals several inconsistencies in how lifetime management is exposed to users. These should be resolved before the 1.0 stable release.

Inventory

Inconsistencies

1. Stream.from_handle cannot opt into keeping an owner alive

• Buffer.from_handle accepts owner= to hold a Python reference and prevent GC of the foreign allocator.
• Kernel.from_handle accepts mod= to hold a reference and prevent GC of the parent ObjectCode/library.
• Stream.from_handle has no equivalent parameter. It creates a borrowed stream with no way for the user to tie lifetime to an owner object.

The internal machinery already supports this — create_stream_handle_with_owner() in C++ accepts a Python owner and does Py_INCREF/DECREF. But from_handle() only passes the ephemeral _stream_holder wrapper as the owner, not the user's actual owner object.

Suggestion: Add an owner parameter to Stream.from_handle, consistent with Buffer.from_handle.

2. Event has no public from_handle()

• Stream, Kernel, and Buffer all expose public from_handle() for wrapping foreign CUDA handles.
• Event only has from_ipc_descriptor(). There is an internal _from_handle() (cdef), but no public way to wrap a foreign CUevent.

Suggestion: Add Event.from_handle(handle) for symmetry, with the same borrowed/non-owning semantics.

3. Kernel.from_handle docstring doesn't clearly document ownership

• Stream.from_handle docstring explicitly says: "Stream lifetime is not managed, foreign object must remain alive while this stream is active."
• Buffer.from_handle docstring explicitly documents all three ownership modes and when the pointer is/isn't freed.
• Kernel.from_handle docstring mentions mod "provides library lifetime for foreign kernels" but doesn't clearly state that the kernel handle itself is non-owning and won't be destroyed on close/GC.

Suggestion: Improve the Kernel.from_handle docstring to match the clarity of the other two.

Additional observation

All from_handle() methods use @staticmethod, while from_ipc_descriptor() / from_gl_*() / from_allocation_handle() use @classmethod. This may be intentional (the latter group uses cls for subclassing support), but worth confirming as a deliberate convention and documenting if so.

-- Leo's bot