Converts from a plain alias to a shell wrapper so the revisions
argument defaults to mm+::@- but can still be overridden.

Assisted-by: Claude Opus 4.6 via pi

diff --git a/.config/jj/config.toml b/.config/jj/config.toml
index 8d0c1a16..9d1124d2 100644
--- a/.config/jj/config.toml
+++ b/.config/jj/config.toml
@@ -106,12 +106,12 @@ tug = ["util", "exec", "--", "bash", "-c", """
   ref=${1:-@}
   jj bookmark move --from "closest_bookmark($ref)" --to "closest_pushable($ref)"
 """, ""]
-stack = [
-  "rebase",
-  "--insert-after", "trunk()",
-  "--insert-before", "heads(closest_merge(@) | mm)",
-  "--revisions"
-]
+stack = ["util", "exec", "--", "bash", "-c", """
+  jj rebase \
+    --insert-after 'trunk()' \
+    --insert-before 'heads(closest_merge(@) | mm)' \
+    --revisions "${1:-mm+::@-}"
+""", ""]
 pr = ["util", "exec", "--", "bash", "-c", """
   gh pr create --head \
     $(jj log -r 'closest_bookmark(@)' -T 'bookmarks' --no-graph | cut -d ' ' -f 1)