[avatar] Add `aria-hidden` to `AvatarFallback`

[battaglr]

• [x] I have followed (at least) the PR section of the contributing guide.

Rationale

AvatarFallback is purely presentational and doesn’t convey meaningful information. Marking it with aria-hidden="true" prevents redundant or confusing announcements.

When an avatar is used inside an interactive element (e.g., a button or link), that element (I think) should provide an accessible name using aria-label or a similar attribute.

Concerns / Questions

Are there cases where the avatar fallback is the only identifier for an entity (user, group, etc.)?

If so, should aria-hidden be applied, depending on whether an aria-label is present?

[pkg-pr-new[bot]]

vite-css-base-ui-example

pnpm add https://pkg.pr.new/mui/base-ui/@base-ui-components/react@3095

pnpm add https://pkg.pr.new/mui/base-ui/@base-ui-components/utils@3095

commit: 5df07ba

[netlify[bot]]

✅ Deploy Preview for base-ui ready!

Name	Link
🔨 Latest commit	5df07bab75f0b03c1e72722150d0810223a73c5e
🔍 Latest deploy log	https://app.netlify.com/projects/base-ui/deploys/6902d32ec2ba8a0008d5ab42
😎 Deploy Preview	https://deploy-preview-3095--base-ui.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.