fix: mermaid racing conditions when multiple diagrams are present

[HugoHSun]

	Fix CX-2822

🧰 Changes

Pages with multiple mermaid diagrams would intermittently render broken on refresh. Two or more diagrams would overlap into the same <pre> element while another would be empty.

The root cause is mermaid's ID generation. It uses Date.now() to generate SVG IDs, and when multiple diagrams are processed in the same millisecond they get identical IDs. Since mermaid uses document.getElementById() to clean up before rendering, a duplicate ID causes it to delete the wrong SVG from the DOM.

Previously, each CodeTabs instance called mermaid.run() independently with all mermaid nodes on the page. Now mermaid nodes are batched into a single mermaid.run() call using a setTimeout(0) to collect all nodes from the same render cycle. Combined with deterministicIds: true, this gives every diagram in the batch a unique ID.

🧬 QA & Testing

https://www.loom.com/share/376c0ae07c0142d083a6cadf99889e9f

Add multiple mermaid charts in a doc and refresh multiple times

• Broken on production.
• Working in this PR app.