chore: migrate os-pm packages to inline syntax, drop pm.yaml/pm.lock

[reyreavman]

What was done

delivery-kit no longer supports the file-based format (pm.yaml/pm.lock) for packages.type=os-pm — only inline syntax is accepted (pkg/config/raw_packages_directive.go: a file path string in spec produces the error use inline package list instead of file path, workdir is forbidden). Examples: test/e2e/sbom/_fixtures/inject/ospm_basic.

• Removed pm.yaml and pm.lock.
• werf.yaml (images-digests image):
  • spec: "pm.yaml" / lock: "pm.lock" → inline spec: [jq==1.8.1]; the version is pinned from the former pm.lock for reproducibility;
  • removed the git: block with includePaths: pm.yaml, pm.lock — it existed solely to deliver those files.
• SKILL.md (werf-to-delivery-kit-migration), section 4: explicitly declares inline-only syntax for os-pm (list of package names, version pinning via name==version), the file-based format is not supported, workdir is forbidden, env is supported. The "Pitfalls" section now clarifies that stageDependencies on manifest/lock files applies only to file-based types — the inline os-pm list affects the stage digest by itself.

Verification

• rg 'pm\.ya?ml|pm\.lock' — no references to pm files remain in configs.
• Inline syntax verified against delivery-kit sources and e2e fixtures on main.