When the decoder hasn't produced a frame in 5s, skip the call to
_playerClient->getImage() entirely and return the cached frame with
unchanged _pts. LabVIEW sees STALE PTS one poll earlier and can
trigger reconnect sooner.
Threshold matches the existing checks on the duplicate-PTS branch and
in areImagesIdentical() so all three stale paths agree. Near-zero cost:
one getLastFrameAgeMs() call before the main path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
