docs: sharpen positioning and retire planning notes

[TacoRocket]

Summary

• rewrite the top of the README around attack paths, pivots, and operator workflow
• simplify CloudFox attribution to a short inspiration note
• add a Dependabot-only dependency sanity workflow
• remove the retired wiki planning/api-mapping tree and document docs boundary rules

Validation

• git diff --check
• pre-push guardrails: ruff check .
• pre-push guardrails: pytest (307 passed, 2 deselected)