❌ #1399 had this — same-length fences don't nest
```python # outer (3 backticks)
prompt = f"""...
```tsx # inner (3) — CLOSES the outer
{component['scaffold']}
``` # now opens a new tsx block
{f"Adapt: {x}" if cond else ''}
"""
``` # this is now stranded prose
→ MDX parses {f"..." ...} as JSX expression → acorn chokes
✅ This PR fixes it — outer fence is one longer
````python # outer (4 backticks)
prompt = f"""...
```tsx # inner (3) — properly nested
{component['scaffold']}
```
{f"Adapt: {x}" if cond else ''}
"""
```` # closes the outer at 4 backticks
→ Inner content stays inside the outer block; mdx compiles cleanly