fix: prevent Angular chat submissions from failing on non-cloneable message metadata (#19333)

## Background

Angular chat submissions could enter an error state with DataCloneError
before invoking the transport when the last message contained function
metadata.

## Root Cause

AngularChatState.snapshot used structuredClone for every submitted last
message. The recorded reproduction confirmed that non-cloneable metadata
caused structuredClone to throw before sendMessages was called.

## Summary

Changed Angular chat snapshots to pass messages through without deep
cloning, added a patch changeset, and removed reproduction-only
artifacts.

## Testing

Added regression tests covering user-message submission and
assistant-message resubmission with function metadata, verifying both
requests reach the transport without errors.

## End-to-end Validation

- `pnpm -C examples/ai-functions exec tsx
src/reproduction/issue-19330-angular-chat-structured-clone.ts` exited
successfully using the unchanged recorded reproduction; both affected
submissions reached the transport without DataCloneError.

## Related Issues

Fixes #19330

Closes #19332

---------

Co-authored-by: ai-sdk-factory <308175966+ai-sdk-factory@users.noreply.github.com>
Co-authored-by: habibthadev <109099706+habibthadev@users.noreply.github.com>