Mermaid charts convert to text on live reload until page refresh

[tuurep]

Description

On live reload (i.e. modifying the mermaid code block) it gets rendered as a regular markdown code block instead of a Mermaid chart.

To Reproduce

Have a document such as

```mermaid
flowchart LR
    A[foo]-->B[bar]
```

which renders as (screenshot):

Start editing the mermaid block, such as

```mermaid
flowchart LR
    A[foo]-->B[bar]
    B-->C
```

It renders as this (screenshot):

until manual page refresh:

Context

• Firefox 133.0
• Arch Linux
• vivify-git (AUR)
  • vivify-server v0.6.3.r0.g5d07d16-1-aur