fix: silent default test output; verbose controlled by SOURCETEST_VERBOSE env var

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.

scripts/test-sources.sh

@@ -232,11 +232,12 @@ ok "Network $NETWORK exists"
 
 SHORT_FLAG=""
 VERBOSE_FLAG=""
+VERBOSE_ENV=""
 FLAGS=""
 while [ $# -gt 0 ]; do
   case "$1" in
     -short) SHORT_FLAG="-short"; FLAGS="$FLAGS -short"; shift ;;
-    -v)     VERBOSE_FLAG="-v";   FLAGS="$FLAGS -v";     shift ;;
+    -v)     VERBOSE_FLAG="-v";   FLAGS="$FLAGS -v"; VERBOSE_ENV="-e SOURCETEST_VERBOSE=1"; shift ;;
     *)      break ;;
   esac
 done
@@ -262,6 +263,7 @@ set +e
 docker run --rm \
   --network "$NETWORK" \
   -e FLARESOLVERR_URL=http://flaresolverr:8191 \
+  $VERBOSE_ENV \
   -v "$REPO_ROOT":/workspace \
   -v goyomi_go_mod_cache:/go/pkg/mod \
   -v goyomi_go_build_cache:/root/.cache/go-build \