docs: expandable content feedback from users

[mmcallister]

We've gotten periodic feedback about content being hidden and missed in the expandable sections. Some examples:

the two sections about security best practices and shell completion are hidden in collapsible section, which is not obvious at first. Consider removing the collapsible/detail markdown directive. (/docs/reference/cli/)

Going forward, we shouldn't put content like warnings, best-practices, or similar important details in expandable sections as it could be missed.

what ports and address does the agent need? e.g. how to lock down outbound connections from agents to proxy (/docs/reference/networking/)

For this one, the info is there but it is hidden at first; it’s the only piece on the page presented in a collapsible section.