testdata: seed sandbox clean child

Stack Demo · Stack Demo · commit 3f47a3b92f64 · 2026-03-25T16:14:19.000-04:00
diff --git a/_test_data/sandbox/clean/child.txt b/_test_data/sandbox/clean/child.txt
@@ -1,3 +1,3 @@
 clean stack: child branch
 purpose: child PR on top of sandbox-clean-base
-marker: 7262f98
+marker: e13a28c
