Treat matching kernel headers as a base system guarantee

(cherry picked from commit 24417bf191)

migrations/1789444024.sh

@@ -3,6 +3,8 @@ echo "Install missing headers for the Omarchy or T2 kernel"
 # Fresh ISO installs mark earlier migrations complete, so the kernel migration
 # cannot repair headers omitted by those installers. Package installation is
 # idempotent when another user has already applied this repair.
-if omarchy-pkg-present linux-omarchy || omarchy-pkg-present linux-t2; then
-  omarchy-pkg-add-kernel-headers
-fi
+for kernel in linux-omarchy linux-t2; do
+  if omarchy-pkg-present "$kernel"; then
+    omarchy-pkg-add "$kernel-headers"
+  fi
+done