Embedded form deployment in camunda-standalone-tomcat

I got error in start form Form failure: The context path is either empty or not defined.

I have read this post. and tried the methods mentioned inside: Embedded form failure

I am using 7.15 camunda-tomcat-standalone distribution: camunda-bpm-platform/distro/tomcat/webapp-standalone at 7.15.0 · camunda/camunda-bpm-platform · GitHub

I have such project structure:

and I refer to my form this way: embedded:app:forms/useless-form.html.
what did I do wrong?