docs: add EvalOps action factory agent rails

[haasonsaas]

Summary

• add EvalOps-on-EvalOps agent practice rails to org-level AGENTS.md
• encode live-evidence-first work, accounted blockers, post-merge verification, Cerebro action-factory records, and bounded polling
• explicitly preserve the no CodeQL / no GitHub Code Scanning / no SARIF upload policy

Live context

• Checked open evalops/.github PRs: none
• Relevant open issues: Retire GitHub-managed CodeQL tombstone workflows #118 CodeQL tombstone workflows, [codex] Guardrail backlog: Workflow shell footgun (workflow-shell-footgun) #69 workflow shell footguns, [codex] Guardrail backlog: Release train drift (release-train-drift) #71 release train drift

Test Plan

• git diff --check
• inspected rendered Markdown diff for AGENTS.md

Rollback

• Revert this PR to remove the new org-level agent practice section.