Markdown Renderer Still Has Hard-Coded Fallbacks For Disabled ExtensionsURL copied
Observed in ContentRenderer.render_block_code:
- It checks runtime handlers first.
- Then it still falls back to hard-coded D2, Cytograph, Cryptograph, Mermaid,
and Tasks renderers.
- Delete all feature fallback branches.
- If a fence has no registered handler, render it as a normal code block.
- This is the key test that disabled extensions are real.