[codex] Remove MI325X runner workarounds

[cquil11]

• Remove stale benchmark log cleanup from the MI325X AMD launcher.
• Allow Slurm to schedule chi-mi325x-pod1-121.ord.vultr.cpe.ice.amd.com.

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Note

Low Risk
Launcher-only script changes with no auth or data handling; main risk is jobs landing on a previously excluded node if the enroot/NFS issue regresses.

Overview
Removes temporary mitigations from runners/launch_mi325x-amds.sh now that the underlying issues are addressed.

Slurm scheduling: salloc no longer passes --exclude for chi-mi325x-pod1-121, so that node can receive jobs again.

Cleanup: Deletes cleanup_stale_benchmark_logs and all invocations (startup and on EXIT), including the benchmark_logs removal under GITHUB_WORKSPACE. The exit trap only cancels the job and preserves the exit code.

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[claude]

Claude finished @cquil11's task in 47s —— View job

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PR Review: Remove MI325X runner workarounds

• Gather context and review changes
• Validate against review guidelines
• Post review

LGTM — no blocking issues found.

This is a clean removal of two workarounds that are no longer needed:

1. Removed cleanup_stale_benchmark_logs function and its calls — eliminates the sudo rm -rf / rm -rf cleanup of $GITHUB_WORKSPACE/benchmark_logs from both the startup path and the EXIT trap.
2. Removed --exclude=chi-mi325x-pod1-121.ord.vultr.cpe.ice.amd.com from salloc — re-enables Slurm scheduling on this node now that the underlying enroot/aufs issue (originally tracked via [Klaud Cold] Update gptoss-fp4-mi325x-vllm vLLM ROCm image to v0.21.0 #1467/[Klaud Cold] Update kimik2.5-int4-mi325x-vllm vLLM ROCm image to v0.21.0 #1468/[Klaud Cold] Update minimaxm2.5-fp8-mi325x-vllm vLLM ROCm image to v0.21.0 #1469) has been resolved.

The resulting script is simpler and the changes are straightforward with no functional risk.