fix: Google file uploads fail strict TypeScript 5.9 compilation (#19533)

## Background

The Google file upload source failed strict TypeScript 5.9 compilation
with TS2769 when assigning its binary upload body to RequestInit.

## Root Cause

The upload passed Uint8Array<ArrayBufferLike> directly to fetch, while
TypeScript 5.9 DOM types require BodyInit array-buffer views to be
ArrayBuffer-backed; the recorded diagnostic and successful post-fix
TypeScript 5.9 replay confirmed this.

## Summary

Normalized upload bytes to an ArrayBuffer-backed Uint8Array, copying
only inputs backed by another buffer type, and added a patch changeset.

## Testing

Updated the Google Files upload regression test to verify
SharedArrayBuffer-backed input is sent with unchanged bytes in an
ArrayBuffer-backed body.

## End-to-end Validation

- `pnpm -C examples/ai-functions exec tsx
src/reproduction/issue-17441-google-files-fetch-body-type-compatibility.ts`
— exited successfully and reported that TypeScript 5.9 accepts the
upload body.

## Related Issues

Fixes #17441

Closes #19516

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Co-authored-by: ai-sdk-factory <308175966+ai-sdk-factory@users.noreply.github.com>
Co-authored-by: Gregor Martynus <39992+gr2m@users.noreply.github.com>
Co-authored-by: KushalXCoder <168859142+KushalXCoder@users.noreply.github.com>