[vue-query] `shallow: false` can lead to identity hazards

[JoaoPedroAS51]

Describe the bug

Hi!

The changes introduced by #7733 can lead to identity hazards in dev mode, when shallow option is set to false. Since the state is now shallowReactive, only the root level object is proxied. Using readonly makes nested objects proxied as well.

Your minimal, reproducible example

https://play.vuejs.org/#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

Steps to reproduce

Check the comparison in the playground

Expected behavior

Nested objects are proxied in dev mode when shallow option is set to false, but not proxied in prod mode. I expect dev and prod to behave the same.

How often does this bug happen?

None

Screenshots or Videos

No response

Platform

• OS: macOS
• Browser: Chrome
• Version: 128.0.6613.120

Tanstack Query adapter

vue-query

TanStack Query version

v5.56.2

TypeScript version

No response

Additional context

No response