Update README with WARNING

[kathrinmotzkus]

This README is from the developer of rtk-ai. rtk-rust-ai is a clone of rtk-ai and under investigation. It seems that rtk-ai was completely created by AI (Claude) and the developer doesn't have a clue about what he sent into the AI-world.

Summary

Test plan

• cargo fmt --all && cargo clippy --all-targets && cargo test
• Manual testing: rtk <command> output inspected

Important: All PRs must target the develop branch (not master).
See CONTRIBUTING.md for details.

[CLAassistant]

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[pszymkowiak]

[w] wshm · Automated triage by AI

📊 Automated PR Analysis

📝 Type	docs
🟢 Risk	low

Summary

This PR adds a warning banner to the top of the README.md claiming that rtk-rust-ai is a clone of rtk-ai and is under investigation. The change consists solely of inserting an HTML h1 element at the very beginning of the README. No code changes are involved.

Review Checklist

• Tests present
• Breaking change
• Docs updated

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Analyzed automatically by wshm · This is an automated analysis, not a human review.