fix(react): support strict pnpm type resolution

[raashish1601]

Fixes #3865.

Summary

• declare @types/react as an optional peer dependency for @headlessui/react so strict pnpm installs link the React types where the package declarations need them
• make useFloatingReference() export the UseFloatingReturn['refs']['setReference'] type explicitly so the generated declarations stop leaking a direct @floating-ui/react-dom import from a transitive dependency

Validation

• reproduced the published-package failure in a fresh strict pnpm consumer (hoist=false) where @headlessui/react@2.2.9 fails tsc --noEmit
• built @headlessui/react locally under Git Bash and confirmed packages/@headlessui-react/dist/internal/floating.d.ts no longer imports @floating-ui/react-dom
• reran the same strict pnpm consumer against the local package and confirmed corepack pnpm exec tsc --noEmit passes

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[baraknaveh]

It would probably make sense to synchronize this with the react dep itself, i.e.,

"@types/react": "^18 || ^19 || ^19",

[baraknaveh]

Thanks for the PR!