claude: revert extract.py to return JSON

assemble markdown in TS

override the executable cell regex to accept

```python {.marimo}

to discuss: also accepts quarto executable syntax

```{marimo}

but should that be

```{marimo-python}

?

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gordonwoodhull

_extensions/marimo/command.py

@@ -30,8 +30,7 @@ def extract_command(header: str) -> list[str]:
     with tempfile.NamedTemporaryFile(
         mode="w", delete=False, suffix=".txt"
     ) as temp_file:
-        # Add html2text as additional dep for PDF HTML-to-markdown conversion
-        flags = construct_uv_flags(pyproject, temp_file, [], ["html2text"])
+        flags = construct_uv_flags(pyproject, temp_file, [], [])
         temp_file.flush()
     return ["run"] + flags