Rust LLM Policy

Recently data.table added a LLM policy file, AGENTS.md.

That PR mentions the blog, rust-lang/rust is adopting an LLM policy.

These are similar to the documents I recently wrote:

• R GSOC FAQ AI Policy
• animint2 CONTRIBUTING.md Avoid/declare AI code generation

Interestingly, the Rust blog emphasizes

• disclosure of AI generation in issue and PR comments (we want responses from a person, not a LLM)
• creating a community of experts, not a repo of artifacts