go test -json implicitly sets testing.Verbose()=true, so the old guard
always printed manga lists through the script. Switched to an env var
(SOURCETEST_VERBOSE=1) set by the script only when -v is passed.
When -v is passed, test-sources.sh passes it through to go test -v.
sourcetest.Run uses testing.Verbose() to print the full manga list
from GetPopularManga and GetLatestUpdates, showing title + URL.
achmad