Clean up current documentation status

[willamhou]

Summary

• Refresh README gap/evidence wording across English, Chinese, and Japanese docs after PR Record multi-file external fixture evidence #16.
• Replace stale current-status, roadmap, MVP, and architecture pages with concise current-state docs.
• Document external fixture post-validation evidence requirements and add a superpowers archive notice.

Validation

• git diff --check
• node scripts/check-secrets.js
• cargo fmt --check
• stale status keyword scan for old 39-run / 70-case / DNS-blocker wording

[github-actions]

DeepSeekCode review of PR #17 (Clean up current documentation status)

Let me fetch the actual PR diff from GitHub since the local workspace doesn't have the PR changes.