docs: refresh public release status

[daichunghy]

Summary

• refresh the README status date to 2026-08-30
• keep the GitHub alpha.7 and npm alpha.6 distinction visible
• keep the no-external-consumer and no-pilot boundary explicit

Verification

• npm run verify passes from origin/main with the README change
• GitHub release and npm dist-tag state were checked live before editing

This is a documentation-only update. It does not publish alpha.7 or change package visibility.