Project avatar fallback doesn't support emoji characters #12441

Description

The avatar component's fallback (used for project icons) doesn't correctly display emoji characters. When a project name starts with an emoji like "😀MyProject", the avatar shows a broken character instead of the emoji.

Root Cause

The avatar component uses split.fallback?.[0] to get the first character. JavaScript string indexing with [0] returns individual UTF-16 code units, but emojis use surrogate pairs (two code units). This means "😀"[0] returns only the first half of the surrogate pair, resulting in a broken character.

Regular Unicode characters like Chinese characters work fine because they fit in a single UTF-16 code unit.

Expected Behavior

Emojis should display correctly in avatar fallbacks, just like regular characters.