fix(bedrock): deliver streaming chunks individually instead of in batches

[shivaber]

Description

Fix BedrockModel.stream() delivering chunks in batches instead of individually.

Replace call_soon_threadsafe(queue.put_nowait) with run_coroutine_threadsafe(queue.put()).result() and use a bounded queue (maxsize=1). This blocks the producer thread until each event is delivered to the event loop, preventing callback batching where all chunks were processed in a single event loop iteration.

Root cause: When Bedrock sends chunks in a burst (e.g., multiple chunks in one TCP segment), call_soon_threadsafe scheduled all put_nowait callbacks at once. The event loop processed them all before the queue.get() waiter ran, causing queue depths of 5-6 items and delivering all chunks simultaneously.

After fix: Queue depth is always 0 after each get(), ensuring chunks are yielded one at a time for proper real-time streaming.

Related Issues

Closes #1523

Type of Change

Bug fix

Testing

• Added test_stream_delivers_chunks_individually regression test that verifies queue depth is 0 after every get() when chunks arrive in a burst

• All 110 existing bedrock tests pass

• Verified with reproduction script: before fix queue depth reached 5-6, after fix always 0

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
  ⠋- [x] I have added an appropriate example to the documentation to outline the feature, o r no new docs are needed
  Thinking...- [x] My changes generate no new warnings
• Any dependent changes have been merged and published

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.