[moetemp]

What was changed

This PR adds the Stream examples and the end-to-end Redis tests, the module doc of temporalio.streams, the Streams changelog fragment and a CODEOWNERS entry.

• Each example follows the Python tab of its API proposal section, and runs as a test on both backends. The ids and task queues come from the test, so the runs don't share them.
• In the UI backend and resume examples, a client creates the Stream and passes its ref to the Workflow. The reader gets it by id with client.get_stream[Turn](chat_id), and matches on r.kind, which narrows the item's type. Its read ends when the creator closes the Stream at the end of async with.
• In the client example, the Workflow gets the ref as data, writes through workflow.to_stream(ref), and passes the same ref on to an Activity.
• The agent example creates its two Streams under its session id, hands out the turns ref through a stream query that returns None before the create, and forwards both refs at continue-as-new. It publishes the done Turn with the reply, then closes, since a close carries no value.
• The Activity example writes through activity.client().to_stream, and uses a fake model client in place of a model call. Its sync Activity is a method of a class that keeps the Worker's client, since a sync Activity has no activity.client().
• The end-to-end tests cover Workflow and Activity writes to one Stream, replays that send no create again, codecs, eviction, retries, continue-as-new and two backends on one client.
• worker_setup.py says that a Worker serves only one backend. Its test checks that a Worker on the migration's client with two backends raises StreamConfigError.
• The changelog fragment covers the whole stack.

Why?

After this PR, feature-streams has the whole API. Upstream merges feature/streams into main once, so main never has half an API. The examples are the API docs until the docs site has Streams.

Open question. CODEOWNERS gives the AI SDK team and the SDK team the Streams paths, temporalio/streams/ included. Which team owns them?

Part of the Streams review series.

Checklist

1. How was this tested:
   • poe lint, poe gen-docs, a regeneration that leaves no diff, the Streams suite on both backends with Redis, and the client, converter, bridge, Replayer, plugin and Nexus caller suites.

[moetemp]

Closed in favor of #381, the combined branch, which has this change.