ci(os-49): add temporary VM validation workflow

[jtoelke2]

Summary

Temporary OS-49 validation PR. This adds a throwaway workflow to collect evidence for VM boot support and non-destructive GPU/VFIO host capability on shared runners. It is not intended to merge.

Related Issue

OS-49 (Linear)

Changes

• Adds OS-49 VM Validation workflow triggered by pull-request/<N> mirror pushes or manual dispatch.
• Runs mise run e2e:vm on linux-amd64-cpu8 and linux-arm64-cpu8 to test actual VM boot on shared CPU runners.
• Probes shared Linux GPU runners for /dev/kvm, NVIDIA PCI devices, IOMMU groups, and VFIO sysfs readiness without binding or unbinding GPUs.

Testing

• Workflow YAML parses locally with Ruby YAML loader.
• mise run pre-commit passes. It was run, but current main fails ssh::tests::launch_editor_returns_friendly_error_when_binary_missing; rerunning that single test reproduced the same unrelated failure.
• E2E tests added/updated if applicable. This PR adds a temporary CI validation workflow; evidence comes from the PR workflow run.

Checklist

• Follows Conventional Commits
• Commit is signed off (DCO)
• Architecture docs updated (not applicable for temporary validation PR)

Cleanup

Close this PR after collecting the VM boot and GPU/VFIO probe results. Do not merge unless the team explicitly decides to keep a permanent version of this workflow.

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