[Feature request] warn user when not running adk web from parent directory of agent projects

I know... "read the docs next time" :)

This added UX frustration for me once I came back to my agent project later (and did not re-read the docs after I bootstrapped my first project or two) and spent ~1 hour trying to troubleshoot why adk web was not able to see my agent.

Pls assume I'm ignorant/lazy and add a warning message in the server logs that tells me something along the lines of "no agents found - please ensure you are in the parent directory containing your agents (not the directory where agent.py is located)"