ci(qualification): add reusable clean-install flow #2974

Description

Add a reusable clean-install qualification flow. The flow consumes an immutable candidate artifact set and a compatible target, installs the candidate through that target's documented package mechanism, verifies the installation, invokes the selected test suites, and cleans up.

The flow must contain no Fedora-, Podman-, architecture-, or suite-specific behavior.

Context

• Parent release pipeline: feat: 0.1.0 release pipeline #2860
• Qualification composition contract: feat(ci): compose release qualification from targets, flows, and suites #2972
• Reusable release artifacts: chore(ci): clean up release pipeline #1683
• Shared driver conformance suite: spike: driver conformance suite for compute drivers #2183

Clean installation is P0 across the initial release qualification matrix. Fedora rootless Podman is the first target, but the same flow must be reusable for other RPM, DEB, Helm, macOS, and Windows targets as their package operations become available.

Definition of Done

• The flow accepts an immutable candidate artifact manifest and a separately defined target.
• It installs the exact candidate artifacts through the target's documented package mechanism without using floating dev artifacts.
• It verifies the installed OpenShell version and candidate identity before running suites.
• It starts or discovers the installed gateway and verifies gateway health.
• It invokes independently selected suites and propagates their pass/fail result.
• It emits machine-readable step results and retains target-provided diagnostics on failure.
• It always invokes target cleanup after success, failure, or interruption.
• The Fedora Podman target requires no flow-specific fork or copied implementation.