Route new PTS producers through Stream V6

[robelest]

Stack

1. Upstream Register Stream V6 storage get-convex/persistent-text-streaming#62 — Stream V6 foundation
2. Producer and lifecycle routing (this PR)
3. Engine-aware bounded reader
4. Browser transport
5. React integration
6. Release certification

This PR lives in the fork so its base can be the fork-owned foundation branch. After upstream get-convex#62 merges, this branch can be opened against upstream main with the same isolated diff.

Summary

• Keep the existing StreamId as a stable facade while creating native V6 storage for every new stream.
• Elect exactly one producer with an atomic OCC claim; duplicate requests return 205 without invoking the writer.
• Persist text through Unicode-safe V6 appendMany batches and mirror PTS lifecycle, inactivity timeout, and deletion transactionally.
• Preserve legacy rows without coreId: they continue using the existing chunk write, status, timeout, and deletion paths with no migration.
• Bound raw response buffering independently from persistence; punctuation, 100 ms, and 16 KiB trigger durable flushes, and unread/canceled consumers cannot stop final persistence.
• Preserve getStreamBody for native streams through a finite compatibility snapshot (4,096 events / 4 MiB); the next PR adds the unbounded-history-safe incremental reader.

No public method signatures or HTTP request shapes change in this layer.

Validation

• 17 tests across component routing and client producer transport
• Build, package/example/Convex typecheck, ESLint, Prettier, and diff checks
• Adversarial follow-up review of lifecycle consistency, exact body limits, cleanup starvation, and raw cancellation

Real concurrent claim and delete/append races remain a release-stack integration gate because convex-test runs transactions serially.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@convex-dev/persistent-text-streaming@7

commit: ea868e5

[robelest]

Closing this premature fork-hosted stack PR. The V6 PTS stack will remain local until it is complete and ready to be submitted natively to get-convex.