Propagation analysis panel now adds a "Tropo duct detected at N/M HRRR
samples along the path" line whenever any HRRR sample flags ducting,
even if the overall mechanism classification doesn't end up pointing at
the duct (e.g. short paths, clear-LoS contacts). Also rewords the map
caveat to invite users with better coordinates to file a suggested
edit — clickable when logged in, otherwise a login link.