Add README, landing page, contributing and security docs

[karanb192]

Summary

• Repo README.md: what it does, the stored-row example from the headless run, install, what makes it safe to run, proof so far, the validator lines and threat model, how it works, what it catches, options, limitations, for teams, contributing, license.
• site/index.html and site/CNAME: a self-contained landing page for redact.aidojo.si in the Anthropic palette with system fonts, dark mode, a working copy button, no external scripts.
• CONTRIBUTING.md (how to run validate and the kit, how to add a rule with fixtures and a source) and SECURITY.md (contact, scope, out of scope).
• plugins/redact/.claude-plugin/plugin.json: the off example id is now generic-secret, a rule that exists.
• plugins/redact/hooks/register.ts: the comment above the prompt.submit hook no longer claims the queue record is covered; it names the headless gap the README documents.

Details

No other tool, mod or proxy is named anywhere in the README or the site. Docs links point at code.claude.com (the docs.claude.com paths returned 404). Every proof claim in the README comes from the mod-builder proof run on Claude Code 2.1.288 and the headless probe; the README says the live interactive edit has not been run.

Test plan

• claude plugin validate plugins/redact --strict passes (run after the comment change: passed)
• claude plugin test plugins/redact: 60 pass, 0 fail (run after the change)
• Open site/index.html locally at desktop and phone width; the copy button copies both install lines
• After merge: Pages source main, folder /site, custom domain redact.aidojo.si; Hostinger CNAME redact to karanb192.github.io