Input
```text
before
\```
after
``` Output AST
- type: CodeBlock
language: text
raw: |-
before
```
after ``` inside CodeBlock body emits literal backtick; escaped triple-backtick line does NOT close the fence
Input
```text
before
\```
after
``` Output AST
- type: CodeBlock
language: text
raw: |-
before
```
after