Function repack

repack(
source: AsyncIterable<Program>,
options: RepackOptions,
): AsyncGenerator<Program>
Rewrites a chunk stream into the chunk shape a provider style expects.
Parameters
- source: AsyncIterable<Program>
  Chunks to repack.
- options: RepackOptions
  Target provider style.
Returns AsyncGenerator<Program>
The repacked chunks.
Example
```
for await (const chunk of delta.repack(upstream, { target: "chat-completions" })) {
  await sink.write(chunk);
}
```