[mryzhov]

Details:

• Add a "Known-Failing and Non-Blocking Checks" section to docs/dev/ci/github_actions/adding_tests.md, explaining why known-failing builds/tests should not run automatically on the initial pre-commit attempt, even if they are non-blocking or outside Overall_Status: they waste runner capacity, create noise, provide no per-change signal and misrepresent validation.
• Recommend running work-in-progress checks on a schedule, either in a dedicated workflow or as a schedule-gated job in an existing workflow. For shared workflows, skip unrelated jobs on the experimental schedule and use a distinct cron expression when the workflow has other schedules.
• Allow opt-in PR validation on a workflow re-run using github.run_attempt > 1, as with draft PR validation. A full re-run also launches the regular workflow, and the condition can match automated re-runs; Smart CI skip rules still apply.
• Recommend tracking and fixing scheduled failures, then enabling the check automatically in pre-commit as a required check in Overall_Status only after it passes reliably. Add the matching pitfall to the ov-github-actions-ci skill.
• Context: [CI] Run C++20 build checks daily instead of in pre-commit #39540 moves the non-blocking C++20 builds to a daily schedule while allowing workflow re-runs.

Tickets:

• CVS-189849

AI Assistance:

• AI assistance used: yes
• The text was drafted with an AI assistant; human validation has not yet been reported.
• git diff --cached --check: passed. This is a documentation-only change, so no build or tests were run.