docs: add agent-generated change policy

[ProfRandom92]

Motivation

• Clarify review and scope requirements for edits produced by coding agents or automation to ensure human oversight and preserve deterministic, auditable PRs.

Description

• Add a concise Agent-generated changes section to CONTRIBUTING.md requiring human review for edits from coding agents (including ChatGPT, Codex, Gemini, and Copilot), mandating generated edits remain within the PR scope and include exact test commands with results, and requiring workflow, dependency, release, security, packaging, or artifact changes to be opened in separate PRs; only CONTRIBUTING.md was modified.

Testing

• Ran python scripts/run_checks.py, which passed, and verified the change was limited to CONTRIBUTING.md.

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Codex Task

[gemini-code-assist]

Code Review

This pull request updates CONTRIBUTING.md to include a policy for agent-generated changes, requiring human review and specific documentation. Feedback highlights a conflict between the new requirement to separate artifact changes and existing policies, suggesting a more precise definition of autonomous agents and clarifying that this rule overrides general artifact inclusion guidelines to maintain audit trails.