Answer the stability review: a code or HTML block swallows the marker line too

corpus/round-trip/commonmark-subset/code-block.json

@@ -6,7 +6,7 @@
       },
       "content": [
         {
-          "text": "SELECT id\nFROM part\nWHERE qty > 0;",
+          "text": "SELECT id\nFROM part\nWHERE qty > 0;\n-- 1. the marker a container start would claim",
           "type": "text"
         }
       ],

corpus/round-trip/commonmark-subset/code-block.md

@@ -2,4 +2,5 @@
 SELECT id
 FROM part
 WHERE qty > 0;
+-- 1. the marker a container start would claim
 ```