The host's CSP map grants allow-forms to /void/rat-* (live nginx, minds.gamecult.org), so native form submission fires its submit event and deliverSubmitEvents has nothing left to do. The manifest link was host-root (/manifest.json, a 404 under /void/rat-*); ./manifest.json resolves under the build's base.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>