bootc-ubuntu-setup: Preserve the original runner OS identity

[cgwalters-bot]

Stacked on #52 (support-ubuntu-2604-signoff); merge that first, then retarget this PR to main.

Fix the OS guard introduced in #53. Installing the Plucky virtualization packages can replace base-files, which rewrites /usr/lib/os-release. The original Ubuntu 24.04 runner then reports 25.04, and our late OS check incorrectly skips the fixed Resolute QEMU.

The affected PR-2290 job records:

17:41:53  IDV=ubuntu-24.04
17:42:49  Unpacking base-files (13.6ubuntu2) over (13ubuntu10.5) ...
17:43:34  idv=ubuntu-25.04
17:43:34  Skipping Resolute QEMU setup on ubuntu-25.04

Capture the original identity in a composite-step output before any package changes. Use it for both #52's Ubuntu 24/26 package selection and the later QEMU guard. Native Ubuntu 26.04 retains its existing package path. Assert the installed QEMU version in the virtualization tests so silently retaining 9.2.1 cannot pass merely because a guest happens to boot.

Validation

• Executed the extracted capture/guard and package-selection shell code with isolated fixtures: initial 24.04 followed by changed 25.04 metadata still selects the intended upgrade; initial 26.04 keeps native packages and skips the foreign-release setup; unsupported initial versions are rejected.
• Verified the version assertion rejects 1:9.2 and accepts 1:10.2 with Debian's actual dpkg.
• Changed-workflow actionlint, extracted shell checks, and whitespace checks passed. The local actionlint version does not yet recognize bootc-ubuntu-setup: Add support for ubuntu-26.04 runners #52's ubuntu-26.04 runner label; those diagnostics are unchanged from the parent branch.
• Separately checked the official native ubuntu:26.04 image: installed QEMU 1:10.2.1+ds-1ubuntu3.2 contains the VHOST_USER_NEED_REPLY_MASK / process_message_reply() ordering fix from upstream 1ba9a522. Its packaged amd64 emulator passed a bounded TCG + slirp + virtio-net startup check. This was not a native arm64 or full bootc integration test.

Generated-by: AI

Implementation and regression fixtures were AI-generated and independently AI-reviewed. Human review and DCO signoff are still required; no Signed-off-by was added automatically.

[Copilot]

🟢 Approval recommended

The implementation directly addresses the reported regression and adds a strict version assertion covering the failure mode.

Pull request overview

Preserves the runner’s original Ubuntu identity across package upgrades, ensuring correct package selection and QEMU installation.

Changes:

• Captures the initial OS identity before package changes.
• Uses that identity for package and QEMU guards.
• Verifies QEMU 10.2 or newer in virtualization tests.

File summaries

File	Description
bootc-ubuntu-setup/action.yml	Preserves and reuses the original runner OS identity.
.github/workflows/test-virtualization.yml	Adds architecture-aware QEMU version validation.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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