build(mosaic): externalize @floating-ui/react instead of bundling it

[alexcarpenter]

Description

Stacked on #9819.

@clerk/mosaic now treats @floating-ui/react as an external dependency instead of inlining it into dist/index.js. It was already listed in dependencies; the tsdown config moves it from alwaysBundle to neverBundle, and check-bundle.mjs now fails the build if the published JS stops importing @floating-ui/react.

Checklist

• pnpm test runs as expected.
• pnpm build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

[vercel]

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Project	Deployment	Actions	Updated
swingset	Ready	Preview	Sep 18, 2026 4:13pm UTC

1 Skipped Deployment

Project	Deployment	Actions	Updated
clerk-js-sandbox	Skipped		Sep 18, 2026 4:13pm UTC

[changeset-bot]

🦋 Changeset detected

Latest commit: 1ad371a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@clerk/mosaic	Patch
@clerk/swingset	Patch

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