fix: defer transport decoding until app is loaded

[LeeWxx]

Fixes #14423

Remote functions with custom transport encoders were failing with "app is not defined" error when called at module level during SSR. The issue occurred because the generated HTML tried to call app.decode() before the app module was loaded.

This fix defers the decoding by storing encoded data in a __deferred array and using placeholder objects {__deferredIndex: n} in the data. After the app module loads, a processDeferred function recursively replaces all placeholders with the actual decoded values. The solution works across all boot paths and includes error handling for decode failures.

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🦋 Changeset detected

Latest commit: 0462552

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

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@sveltejs/kit	Patch

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-14428-svelte.vercel.app/

[dummdidumm]

Thank you, but this doesn't look quite right. I opened a simpler fix, therefore closing in favor of #14434

[LeeWxx]

@dummdidumm Understood, glad there’s a simpler fix 👍