Allow skipping sister repo updates in release.sh

Set SKIP_SISTER_REPOS=1 to bypass the LoopFollow_Second / LoopFollow_Third
update_follower steps. Default behavior is unchanged: both sister repos
are updated as today and missing directories still cause a hard error,
so a forgotten clone in production fails fast.

Author: bjorkert

release.sh

@@ -117,12 +117,20 @@ git diff -M --binary "$MAIN_BRANCH" "$RELEASE_BRANCH"  \
   > "$PATCH_FILE"
 
 cd ..
-update_follower "$SECOND_DIR"
-update_follower "$THIRD_DIR"
+if [ -n "${SKIP_SISTER_REPOS:-}" ]; then
+  echo "⏭️  Skipping sister repo updates (SKIP_SISTER_REPOS is set)"
+else
+  update_follower "$SECOND_DIR"
+  update_follower "$THIRD_DIR"
+fi
 
 # ---------- GitHub Actions Test ---------
-echo; 
-echo "💻  Test GitHub Build Actions for all three repositories and then continue."; 
+echo;
+if [ -n "${SKIP_SISTER_REPOS:-}" ]; then
+  echo "💻  Test GitHub Build Actions for the primary repository and then continue.";
+else
+  echo "💻  Test GitHub Build Actions for all three repositories and then continue.";
+fi
 pause
 
 # --- return to primary path