Fix: Slots without type colors (#7081)

## Summary

Default to a gray

## Screenshots (if applicable)
<img width="416" height="205" alt="image"
src="https://github.com/user-attachments/assets/0eeee37d-f9c1-4893-ae1d-ee20cabf0f46"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7081-Fix-Slots-without-type-colors-2bc6d73d365081499e54e8a10b4b4b02)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

src/constants/slotColors.ts

@@ -1,5 +1,5 @@
 export function getSlotColor(type?: string | number | null): string {
   if (!type) return '#AAA'
   const typeStr = String(type).toUpperCase()
-  return `var(--color-datatype-${typeStr})`
+  return `var(--color-datatype-${typeStr}, #AAA)`
 }