fix: handle nested form submit clicks

[han4wluc]

Summary

• bump route-engine-js to 1.20.4
• make submit-role form containers pass submit behavior to child elements and replace bare child click actions
• complete the current form line before running submitted form actions so valid submits can advance immediately
• add unit coverage and update the form VT spec for the child-click submit path

Testing

• bunx vitest run spec/RouteEngine.form.test.js
• bun run prettier src/stores/constructRenderState.js src/stores/system.store.js spec/RouteEngine.form.test.js vt/specs/form/basic.yaml -c
• bunx vitest run
• git diff --check
• docker run --rm --user 1000:1000 -e RTGL_VT_DEBUG=true -v /home/tk/Code/yuusoft-org/route-engine:/app -w /app docker.io/han4wluc/rtgl:playwright-v1.57.0-rtgl-v1.0.10 rtgl vt screenshot --item form/basic.yaml --wait-event vt:ready --concurrency 1 --timeout 60000
• rtgl vt report --item form/basic.yaml --diff-threshold 0.8

Note: full bun run vt:report captured 111/111 specs, but the full report failed on 14 unrelated non-form reference diffs. The targeted form report passed with 0 mismatches.