[tobixen]

Commit message:

test: wait for search-cache only as long as needed

The integration tests slept the full search-cache delay before every
search, 180 s on Purelymail.  A search now waits only for what is left
of the delay since the last write.  A new filtered-only key on
search-cache, set for Purelymail, also lets plain listings skip it:
there only time-range and text searches lag (probed 2026-10-14), while
Bedework 3 lags in plain listings too.  Bedework 3's search tests pass
in half the time.

Prompt: The purelymail speedup fix, was it only implemented in the caldav-server-tester, or also in the caldav test code?  If the first, then please fix it also in the caldav test code
Followup-Prompt: (chose a per-server search-cache key exempting plain listings, set on purelymail only, after Bedework 3 failed with plain listings exempt everywhere)

Assisted-By: Claude Opus 5.5 <noreply@anthropic.com>
Reviewed-by: Tobias Brox <tobias@redpill-linpro.com>

The caldav-server-tester does the same around CalDAVSearcher.search in python-caldav/caldav-server-tester#25, reading the same filtered-only key.

🤖 Generated with Claude Code