Work on OpenVINO GitHub Actions CI

Guides changes to the regular GitHub Actions CI in this repository: validation and reusable workflows, custom actions, CI scripts, Dockerfiles, and the Smart CI configuration that drives them.

Read the CI developer docs under docs/dev/ci/github_actions first — they are the authoritative, repo-specific reference and this skill is a checklist on top of them. Keep them in sync when behavior changes (see Skill self-improvement). The key pages: