cmd/mbf: jstest: add basic CLI reporter

cmd/mbf/internal/pkgserver/ui/ui.go

@@ -1,7 +1,19 @@
 // Package ui holds the static web UI.
 package ui
 
-import "net/http"
+import (
+	"io/fs"
+	"net/http"
+)
+
+// staticFS is an internal helper to wrap around go:embed's filesystem.
+func staticFS(static fs.FS) fs.FS {
+	if f, err := fs.Sub(static, "static"); err != nil {
+		panic(err)
+	} else {
+		return f
+	}
+}
 
 // Register arranges for mux to serve the embedded frontend.
 func Register(mux *http.ServeMux) {