Add destructive admin action fuzz contract

[chubes4]

Summary

• Add a public wordpress.admin-action contract for destructive disposable admin action execution.
• Execute generic admin-hook, ajax, and admin-post families in runtime-playground with explicit disposable destructive boundary proof.
• Publish descriptor/schema/docs for supported and unsupported families, including editor and browser-random-walk as unsupported in this command surface.

Tests

• npm run build
• node --import tsx tests/wordpress-admin-action-contracts.test.ts
• git diff --check

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.5 via OpenCode
• Used for: Drafting the public contract, runtime handler, tests, docs, and PR description.