Remove orphaned raft::runtime::matrix::select_k declaration

[says1117]

Closes #3028. The header declared raft::runtime::matrix::select_k but had no corresponding implementation anywhere in the repo, was not listed as a CMake build source, and produced no linkable symbols in libraft. Traced to PR #2498 (implementation removed) and PR #2885 (later raft_runtime cleanup that missed this file). The working select_k implementation remains at raft/matrix/select_k.cuh.

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[coderabbitai]

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ℹ️ Recent review info

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Run ID: c75e8cea-f417-4460-814d-93627f17ad86

📥 Commits

Reviewing files that changed from the base of the PR and between 07b5d39 and 4de5f39.

📒 Files selected for processing (1)

• cpp/include/raft_runtime/matrix/select_k.hpp

💤 Files with no reviewable changes (1)

• cpp/include/raft_runtime/matrix/select_k.hpp

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📝 Walkthrough

Summary by CodeRabbit

• Breaking Changes
  • Removed the public select_k runtime API declaration.
  • Applications that depend on this interface may need to update their integrations before upgrading.

Walkthrough

Removed the raft_runtime matrix select_k header and its public function declaration, with no replacement API added.

Changes

Cohort / File(s)	Summary
select_k removal cpp/include/raft_runtime/matrix/select_k.hpp	Removed the public raft::runtime::matrix::select_k declaration and header.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the main change: removing the orphaned select_k declaration.
Description check	✅ Passed	The description matches the change and explains why the header was removed.
Linked Issues check	✅ Passed	Removing the raft_runtime header declaration addresses #3028 by taking select_k out of raft_runtime.
Out of Scope Changes check	✅ Passed	The diff only removes the obsolete header declaration and adds no unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

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• Create PR with unit tests

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[divyegala]

Thank you for the PR!

[divyegala]

/ok to test e23ba3d

[divyegala]

/merge