Pass 0 (unlimited) to m.Search so the mail layer returns all matching
headers; the existing post-filter loop already caps at the caller's
limit, mirroring ListCmd. Add TestSearchLimitCountsVisibleOnly to prove
filtering happens before the cap.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Thread uidv through setup's return value (new uint32 before the cleanup
func) so AckCmd no longer makes a redundant SelectFolder round-trip that
silently returned 0 on failure and recorded acks under the wrong
UID-validity epoch. All four callers updated; read-only callers ignore
the value with _.
steve