docs: add agent-generated change policy (#181)

* docs: add agent-generated change policy

* docs: refine agent-generated change policy wording

Author: ProfRandom92

CONTRIBUTING.md

@@ -44,5 +44,8 @@ Any proposal that expands scope beyond deterministic replay-integrity validation
 ## Merge Policy Summary
 Keep PRs small, focused, and auditable. Separate governance/docs updates from core logic changes. Core logic updates require tests and green CI before merge readiness.
 
+## Agent-generated changes
+Changes primarily authored by autonomous coding agents or automated workflows (including ChatGPT, Codex, Gemini, and Copilot) require human review before merge. These edits must stay within the approved PR scope and include exact test commands with their results. To preserve audit trails for automated edits, put workflow, dependency, release, security, packaging, or artifact-only changes into separate PRs when they are not required outputs of the same fixture, validator, or artifact-generator change.
+
 ## Evidence-Index Reminder
 If committed evidence artifacts change, the evidence index must be updated or explicitly confirmed unchanged with rationale in the PR.