Reject cross-device streams in acquireExternalStream

[scal444]

acquireExternalStream validated a caller-supplied stream handle with cudaStreamQuery, which reports whether the stream is live, not which device owns it. CUDA permits querying a stream that belongs to another device in the same process, so a foreign stream returned cudaSuccess and was accepted. The cross-device rejection the function advertises was therefore never actually happening.

Resolve the stream's owning device and compare it against the current device. cudaStreamGetDevice does this directly but requires CUDA 12.8, above our supported floor, so below that fall back to probing with an event: an event and the stream it is recorded into must share a CUDA context, so recording an event created on the current device fails with cudaErrorInvalidResourceHandle when the stream belongs to another device.

The driver API (cuStreamGetCtx) was avoided deliberately: it changes signature in CUDA 13 and would add a libcuda link dependency.

DeviceTest.AcquireExternalStreamWrongDevice covers this but only runs with 2+ GPUs, which is why it went unnoticed until it failed in multi-GPU CI.

[greptile-apps]

Greptile Summary

This PR strengthens external CUDA stream validation and aligns test includes with the repository’s include convention.

• Resolves a stream’s owning device directly with CUDA 12.8 or newer.
• Uses an event-based device-context probe on older CUDA versions.
• Rejects valid foreign-device streams while preserving default and same-device streams.
• Converts FMCS test includes to repository-root-relative paths.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The new ownership checks preserve valid default and same-device stream handling while rejecting foreign-device streams, and the changed test includes resolve through the established project-root include path.

Important Files Changed

Filename	Overview
src/utils/device.cpp	Adds compatible cross-device stream ownership validation without exposing a concrete correctness regression.
tests/test_fmcs_primitives.cu	Updates local includes to the repository-root-relative convention supported by the target’s include configuration.

_{Reviews (1): Last reviewed commit: "Reject cross-device streams in acquireEx..." | Re-trigger Greptile}

[evasnow1992]

Thank you for fixing the test failure.