Add target repository Claude prompt to READMEs

[hun99999]

Summary

• add a copy-paste Claude Code prompt to every README for applying guardrails inside a target repository
• reference the public repository URL instead of Hun's local path
• clarify that optional tool inventory should run from a read-only agent-bootstrap clone when available
• add README tests that enforce the public URL prompt and prevent local path leakage

Verification

• python3 -m unittest tests.test_readme_docs -v
• python3 -m unittest discover -s tests -p 'test_*.py'
• python3 scripts/check_private_paths.py
• git diff --check
• python3 scripts/audit_agent_stack.py