chore: add changeset for Vitest client environment breaking change

[Ntale3]

Changes

• Adds changeset documenting the removal of the Vitest workaround for client environment imports
• This breaking change requires users to configure Vitest with an SSR environment (node) when testing Astro component rendering
• The code change was already implemented in the next branch; this PR only adds the changeset to document the breaking change

Testing

No code changes were made in this PR - only a changeset was added to document an existing breaking change. The implementation is already present in the next branch where Astro components are stubbed in client environments (see packages/astro/src/vite-plugin-astro/index.ts lines 263-274).

Manual testing was performed on the next branch with similar changes to verify the behavior:

• ✅ Astro components render correctly in node environment
• ❌ Astro components are stubbed in jsdom/happy-dom environments (as expected)

Docs

I made the documenation changes already withastro/docs/pull/12808.

/cc @withastro/docs maintainers for feedback!

The changeset includes comprehensive migration instructions for affected users, covering:

• Who is affected by this change
• How to update vitest.config.ts to use node environment
• Advanced workspace configuration for projects testing both Astro components and browser code

Closes #14895

[changeset-bot]

🦋 Changeset detected

Latest commit: 4b4ec97

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[Ntale3]

@florian-lefebvre the documentation for the the workaround fix hasnt been merged yet but i believe the link hash will eventually be here https://v6.docs.astro.build/en/guides/testing/ since its a testing change correct me if am wrong before i make the next PR

[ematipico]

Sounds good then. Feel free to apply the suggestions and update the link

[florian-lefebvre]

@Ntale3 no need to make another PR! You can just click on commit suggestion.

And we still want to point to the upgrade guide, which itseld will point to the testing docs section.

You'll only be able to update the link once the docs PR is finalized, I left a bunch of comments there

[sarah11918]

I have updated Florian's suggestion with the full link to the upgrade guide now that it's known.

[sarah11918]

I am going to go ahead and accept Florian's change, then I think this should be ready to merge?

@Ntale3 - for future PRs, you can see the image of the "commit suggestion" button from Florian's post. When a maintainer makes a suggestion (that you agree with 😄 ) you only need to press that button and type a commit message. Maintainers are also allowed to perform that action on your behalf, so I'm doing that now so we can resolve this PR before the weekend, and Florian and I both go on holidays for two weeks! 🥳

[delucis]

I see @sarah11918 took care of applying my suggestion, so this should be ready to merge.

Thanks again for helping out on this one @Ntale3!

[Ntale3]

@florian-lefebvre @delucis @ematipico and @sarah11918 i really appreciate you help.
Looking forward to another collaboration soon
Thank you guys!