The search window could be easily immensively better with a few minor changes

The search is always a huge pain point, so here are a few suggestions that would improve it massively for my daily usage:

1. Turn on server-assisted search per default. Searching just the local cache is completely useless in 90% of the cases and nobody expects it to just search that
2. Show a really big, clear indicator when search hasn't finished yet. It is currently almost impossible to safely distinguish between zero results, and the search still going on
3. During e-mail polling going, the server-side search will quietly fail. Not only is it super annoying that it just won't work, it's not even obvious - again, looks like zero search results! At the very least there should be a really obvious indicator, but what should really happen is that the poll gets interrupted instantly and the search gets executed, and then the polling can go back to doing whatever

Actual behavior

None of the things above, and as a result, the search is always a huge pain and extremely unreliable to use

Steps to reproduce

1. Use search

Environment

K-9 Mail version: 5.600 (latest on f-droid I believe)

Android version: 7.1.1

Account type (IMAP, POP3, WebDAV/Exchange): IMAP

No files, tests, or specific entry points are identified. Start by tracing the search flow and its interaction with IMAP server-assisted search and e-mail polling on Android. The work is complete when the three requested behaviors are implemented and the UI clearly distinguishes pending, failed, and empty searches.