* fix(bedrock): stop buffering streamed tool-call argument deltas
Two issues made Bedrock tool-use streaming arrive as a single end-of-stream
burst through LiteLLM while plain text streamed fine.
First, the anthropic-beta allowlist mapped fine-grained-tool-streaming-2025-05-14
to null for bedrock and bedrock_converse, so the header was silently stripped.
Without that beta, Anthropic models on Bedrock buffer tool input server-side and
emit all toolUse.input deltas at once (verified against converse-stream and
invoke-with-response-stream directly). Bedrock accepts the beta via
additionalModelRequestFields.anthropic_beta, so it is now forwarded.
Second, the streaming reads re-chunked the AWS event stream with
iter_bytes(chunk_size=1024). httpx's ByteChunker only releases full 1024-byte
blocks, so the small early events (messageStart, contentBlockStart, first
deltas) sat in the buffer until enough bytes accumulated, pushing
time-to-first-byte from ~1.4s to ~8.5s on buffered tool-use streams. The
default is now no re-chunking; an explicit stream_chunk_size is still honored.
* test(bedrock): cover explicit stream_chunk_size on sync invoke path
* test(bedrock): cover stream_chunk_size plumbing through converse completion
* test(bedrock): cover stream_chunk_size default in legacy BedrockLLM streaming
* test(bedrock): merge converse handler tests into existing mapped test file
pytest imports test modules by basename in non-package test dirs, so the new
tests/test_litellm/llms/bedrock/chat/test_converse_handler.py collided with
the pre-existing tests/test_litellm/llms/chat/test_converse_handler.py and
broke collection in CI. Move the new tests into the existing file
