#7435 fix(ui): keep modal popovers interactive

Summary

• keep portaled popovers interactive when they open inside modal content
• add regression coverage for modal option selection and preserve non-modal behavior

Type of Change

• Bug fix

Testing

• bun --filter @sim/emcn test
• bun --filter @sim/emcn type-check
• bun run lint:check
• bun run check:audits
• bun run apps/sim/scripts/check-block-registry.ts origin/staging

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)