Pinned the stream Core and regenerated the stream api protos.

[moedash]

This PR pins the Core that carries server-side streams and regenerates the Python protos from it.

What changed?

• temporalio/bridge/sdk-core points at the stream Core layer.
• Everything else is what poe gen-protos produces from that pin: StreamSlice, StreamRange and StreamStartPosition in temporal.api.stream.v1, the two stream commands, events and failed causes, stream_slices and consumed_stream_ranges on the poll and completion messages, the DeliverStreamRecords job, and the SubscribeStream and AppendStreamRecords commands. The pin forces the bridge visitor changes too.

Part of AI-198 (epic AI-37).

Why?

The native stream layers need these types before any of their code can exist. Keeping the pin and its regen apart means the next PRs show only hand-written code. The numbers follow the channel's: the stream values sit right after the channel values everywhere both touch.

How did you test it?

Link to a test plan if any -

• Unit Tests
• Staging
• End to End Tests

The bridge builds, and cargo clippy -- -D warnings and poe lint are clean. A second poe gen-protos leaves the tree as committed. The client, activity, workflow, replayer, visitor and streams suites pass on the dev server the fixtures start. Nothing uses the new types yet.