fix: handle target attribute on remote form redirects

[ai-man-codes]

closes #15197

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Problem

Remote forms with target="_blank" did not open the redirect destination in a new tab. Instead, the current tab would navigate to the redirect URL, making target="_blank" completely ignored for both internal and external redirects.

Solution

Check the form element's target attribute before deciding how to navigate. If it's _blank or _new, use window.open() instead of _goto()

I have ran all the tests and there were no issues.

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🦋 Changeset detected

Latest commit: ee1a10b

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

This PR includes changesets to release 1 package

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@sveltejs/kit	Patch

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