Updates the Stan submodule to 99a5b9d70.

stan-buildbot · stan-buildbot · commit ae3c25e6703f · 2025-08-11T14:27:03.000-04:00
diff --git a/stan b/stan
@@ -1 +1 @@
-Subproject commit c89d0bf2a8b7697bf4e1fef376c0cbaaed758b5e
+Subproject commit 99a5b9d70836e1133814bc3dce847ea08c5ccd47
