ci(CI-CD): 👷 add one aggregating required status check

[baxyz]

Summary

• Adds a required job to pr-validation.yml that depends on every blocking job (conventional-commits, version-bump-check, test-features, test-scenarios, shellcheck) and fails if any of them failed or was cancelled.
• Its check name, Required checks passed, is the one name to add as a required status check on the main ruleset — stable even though test-features/test-scenarios fan out into a matrix whose individual check names shift as it changes.

Why

The main ruleset (Settings → Rules → main) has pull_request, code_quality, deletion and non_fast_forward rules but no required_status_checks rule — nothing currently blocks a merge on red CI. Same gap found and fixed in helpers4/rust this week.

Test plan

• CI green on this PR, then add Required checks passed as a required status check in the main ruleset.

🤖 Generated with Claude Code

[github-actions]

✅ PR Validation Passed

All checks passed!

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📋 Pipeline Status

	Job	Status
✅	🧾 Conventional Commits	passing
✅	🔖 Version Bump	passing
✅	🧪 Feature Tests	passing
✅	🧪 Scenario Tests	passing
✅	🐚 ShellCheck	passing

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_{🤖 Generated by @helpers4 CI • 2026-09-24}