Update nvForest to follow RAFT/RMM adopting cuda::stream_ref

[chyunsu3]

Update nvForest according to rapidsai/rmm#2372 and NVIDIA/raft#3129. Both changes landed in the 26.10 branch, so this PR also targets 26.10.

• rmm::cuda_stream_view is now deprecated; we need to include <rmm/cuda_stream_view.hpp> explicitly now.
• get_next_usable_stream() now returns cuda::stream_ref instead of rmm::cuda_stream_view

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 1bba6d6 and 170b664.

📒 Files selected for processing (2)

• cpp/include/nvforest/detail/owning_buffer/gpu.hpp
• cpp/include/nvforest/handle.hpp

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📝 Summary

Summary by CodeRabbit

• Bug Fixes
  • Improved GPU stream handling for better compatibility with current stream interfaces.
  • Added the required support for GPU owning-buffer stream operations.

Walkthrough

The PR adds the RMM CUDA stream view header and changes GPU handle stream extraction from .value() to .get().

Changes

GPU stream handling

Layer / File(s)	Summary
GPU stream interface updates cpp/include/nvforest/detail/owning_buffer/gpu.hpp, cpp/include/nvforest/handle.hpp	The owning-buffer implementation includes rmm/cuda_stream_view.hpp. The GPU handle constructs cuda_stream from get_next_usable_stream().get().

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

Suggested reviewers: csadorf

Merge Risk: ⚪ Minimal · up to 170b6

The CUDA stream API update and required header inclusion are consistent with the stated changes.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: updating nvForest to follow RAFT and RMM adoption of cuda::stream_ref.
Description check	✅ Passed	The description directly explains the RMM and RAFT compatibility updates, including the explicit header include and the cuda::stream_ref API change.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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