Report host_numa virtual memory as host-accessible

[LeSingh1]

A VirtualMemoryResource configured with location_type="host_numa" or "host_numa_current" reports is_host_accessible is False and is_device_accessible is False — it claims the memory is reachable from nowhere.

__init__ classifies host-located resources with a substring test:

# Matches ("host", "host_numa", "host_numa_current")
if "host" in self.config.location_type:
    self.device = None

but is_host_accessible used exact equality:

return self.config.location_type == "host"

Both were introduced in cec0efb (#2016) and disagreed from the start. The answer propagates to Buffer.is_host_accessible, which forwards straight to the memory resource, so anything choosing CPU vs GPU from a buffer — DLPack/StridedMemoryView device selection, copy validation — sees the wrong answer.

host_numa_current is a working configuration today: the driver ignores location.id for that type, so the resource allocates fine and only the reported accessibility is wrong.

The fix gives both sites a shared _HOST_LOCATION_TYPES frozenset so they cannot drift again. VirtualMemoryLocationType is a StrEnum, so membership behaves identically for raw strings and enum members. is_device_accessible is deliberately left alone.

On verification, plainly: I have no GPU and no cuda.bindings build here, so nothing under cuda_core/tests/ can even import and I did not run the new test. What I did run is the old and new expressions plus __init__'s classifier extracted against a verbatim copy of the enum — that reproduces both NUMA types returning False on both properties before the change, and agreement with __init__ for all four members after. The regression test is GPU-gated by construction and will fail on main for the two NUMA parameters.

NOTE: developed with the assistance of an AI coding agent. The new test carries @pytest.mark.agent_authored per AGENTS.md. I reviewed and verified the change before submitting.

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