Replayed the native stream commits onto the unified Core.

[moedash]

This PR replays the native stream commits onto the unified Core, so one Core speaks both stream prototypes.

What changed?

• The commits are the main lineage's stream commits in their order: the stream api, the DeliverStreamRecords job, the two command machines and their tests, delivery and replay re-supply with their tests, and the changelog entries. Review the stream content on those PRs. This PR is where the two lineages meet.
• The stream items sit next to Max's external stream family. The job and command numbers are the same as the main lineage's: deliver_stream_records at 22, subscribe_stream at 31 and append_stream_records at 32, after the channel's 21, 29 and 30. workflow_stream_channels stays at 33.
• The channel machines, the fold and the scheduled-event guard are the ones already on this branch. The main lineage's case that checks notifications come ahead of a stream range lives in core_tests/channels.rs, which this lineage doesn't have, so it stays there.
• The changelog gets the stream entries only. The channel entry belongs to the main lineage.
• A last commit drops the explicit compile root for the record envelope. The command and history protos import stream/v1 from here on, so protoc reaches it through them, as on the main lineage.

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

Why?

One Core that speaks both prototypes lets one Python build run every provider. Replaying the commits keeps the native series out of a second merge, since its branch shares upstream as a base with this one. The vendored api here matches the main lineage's byte for byte, so both lineages put the same numbers on the wire.

How did you test it?

Link to a test plan if any -

• Unit Tests
• Staging
• End to End Tests

The whole workspace lib suite passes at the head, and so does the coverage reporter run with the ignored tests. cargo fmt --check, cargo lint, cargo test-lint and the CI cargo doc check are clean, and each commit builds. The tree was compared with the earlier all-in-one branch. The stream files match it byte for byte, and the rest differs only by the renumber and the channel files aligned with the main lineage.