fix(migrate): sanitize module name correctly for build dir

migration/migrate_module.sh

@@ -30,7 +30,7 @@ MODULE_ABS="/repo/$(realpath --relative-to="$REPO_DIR" "$MODULE_PATH")"
 
 # Try using app/run_docker.sh; if it fails, fall back to direct docker run using the built image.
 # Use a dedicated build dir per-module to avoid permission issues on /repo/build created by earlier runs.
-SANITIZED_MODULE_NAME=$(echo "${MODULE_PATH}" | sed -e 's#/##_g' -e 's/[^A-Za-z0-9_.-]/_/g')
+SANITIZED_MODULE_NAME=$(echo "${MODULE_PATH}" | sed -e 's#/#_#g' -e 's/[^A-Za-z0-9_.-]/_/g')
 BUILD_DIR="/repo/build_migrate_${SANITIZED_MODULE_NAME}"
 
 if ./app/run_docker.sh "$REPO_DIR" -- bash -lc \