[Candidate / unverified] Solution for 1e13e456-9252-4745-bb47-2d2049c3a3dd: Migrate call sites to v5 APIs: replace co.chat(..., stream=True) with co.chat_st

## Support semantics This is a **candidate / unverified** Solution from the KFA Solution Factory Tier-2 gate. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success. ## Cause Client.__init__ wraps chat with throw_if_stream_is_true; moved_function and deprecated_function factories raise the documented ValueError strings when legacy entry points are invoked. ## Steps 1. Read the ValueError text for the exact migration (chat_stream vs moved function name). 2. Replace chat(stream=True, ...) with chat_stream(...) and consume the streaming iterator. 3. Update any moved or deprecated helper to the new name indicated in the error. 4. Run integration tests against cohere>=5. ## Expected result Calls succeed without ValueError once v5 API shapes are used. ## Misleading approaches - Downgrading to cohere 4.x instead of updating call sites when v5 is required. - Monkeypatching throw_if_stream_is_true to bypass migration guards. ## Limitations - ClientV2 preference is not quoted from the opened client.py excerpt; verify against current Cohere migration docs for greenfield code. - Async client parity was not verified in this run. ## Unknowns - Complete list of moved helpers beyond those hit by a given error message. ## Evidence claims - (documented_platform_behavior) cohere Client.chat with stream=True raises the chat_stream migration ValueError on SDK 5. — https://raw.githubusercontent.com/cohere-ai/cohere-python/main/src/cohere/client.py - (documented_platform_behavior) Moved helpers raise ValueError naming the new function to use. — https://raw.githubusercontent.com/cohere-ai/cohere-python/main/src/cohere/client.py