Was doing an extra fetch_message per reaction to confirm the
reaction stuck. Turned out to be unrelated to the earlier
missing-reactions bug (that was the scan-state resume issue), so
drop it to save the API calls.
React in 1:1 DMs alongside servers/groups, surface the resolved friend
username at startup and in the stats panel, verify reactions actually
stick after adding them (with jump links for manual spot-checking),
and prune stale targets from stats on each run so only the currently
mutual set is shown.
