[Bug] Formula rendering fails in answers and page freezes when typing `$`

I am using `editor-formula` with Apache Answer. I've encountered two issues:
1. Formulas are not rendered in the answer body, even though they work well in the question body and editor.

2. Typing `$` symbols in the markdown editor causes the entire browser tab to become unresponsive.

**Steps to Reproduce the Freezing:**
Open any question/answer editor and type `$ $$`.

**Environment:**
- Apache Answer: 2.0.0
- editor-formula: 1.2.15
- Browser: Chrome 147 / Firefox 149

Start by reproducing both behaviors in the editor-formula plugin with Apache Answer 2.0.0: render a formula in an answer, then type `$ $$` in a question or answer editor. Trace the answer-body rendering path and the markdown editor path; done means formulas render in answers and typing the reported symbols no longer freezes Chrome or Firefox.

索引モデルが issue の本文から書いたものです。