fix: replace hardcoded font-size 10px/11px with text-2xs Tailwind token (#10604)

## Summary

Replace all hardcoded `text-[10px]`, `text-[11px]`, and `font-size:
10px` with a new `text-2xs` Tailwind theme token (0.625rem / 10px).

## Changes

- **What**: Add `--text-2xs` custom theme token to design system CSS and
replace 14 hardcoded font-size occurrences across 12 files with
`text-2xs`.

## Review Focus

Consistent use of design tokens instead of arbitrary values for small
font sizes.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10604-fix-replace-hardcoded-font-size-10px-11px-with-text-2xs-Tailwind-token-3306d73d365081dfa1ebdc278e0a20b7)
by [Unito](https://www.unito.io)

Co-authored-by: Amp <amp@ampcode.com>

src/components/sidebar/tabs/modelLibrary/ModelPreview.vue

@@ -85,7 +85,7 @@ const modelDef = props.modelDef
   display: inline-block;
   text-align: center;
   margin: 5px;
-  font-size: 10px;
+  font-size: var(--text-2xs);
 }
 .model_preview_prefix {
   font-weight: 700;