Clarify subdirectories listed via `adk web` command

[aarondietz234]

Describe the bug

The documentation at https://google.github.io/adk-docs/api-reference/cli/#adk-web imply that the subdirectories in AGENTS_DIR will be valid agents, though it appears that AGENTS_DIR can be any subdirectory, whether it's a valid agent or not.

The text in the docs:

AGENTS_DIR: The directory of agents, where each subdirectory is a single agent, containing at least __init__.py and agent.py files.

Expected behavior

Verify and clarify the subdirectories in AGENTS_DIR. Thanks!

[koverholt]

Thanks for the issue! Agree that the CLI docs are ambiguous here and should be clarified to match up with actual adk web behavior. In addition to listing all sub-dirs, in my testing adk web does not work with an AGENTS_DIR arg.

The CLI reference docs are generated from the ADK Python CLI docstrings, so the fix would need to happen upstream. I'll transfer this issue to the adk-python repo so that team can take a closer look.

[wyf7107]

Thanks for filing, I will take a look