fix: retry on stream_version race in event store

[sfncore]

Summary

• Fixes race condition in OrchestrationEventStore.append where concurrent appends to the same stream compute identical stream_version via subquery, causing UNIQUE constraint violations
• Adds optimistic retry (up to 3 attempts) on ConstraintError so the losing writer re-reads the incremented version and succeeds

Test plan

• Verify concurrent event appends to the same thread no longer produce PersistenceSqlError: UNIQUE constraint failed
• Confirm single-writer append behavior is unchanged (no unnecessary retries)

🤖 Generated with Claude Code

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Note

Medium Risk
Touches the event persistence write path and changes behavior under contention by retrying inserts, which could mask unexpected constraint failures if mis-scoped. Retry is bounded (3 attempts) and limited to SQL constraint errors, keeping overall risk moderate.

Overview
Improves robustness of event appends under concurrency. OrchestrationEventStore.append now retries the insert up to 3 times when the database returns a SQL ConstraintError, reducing failures from races where concurrent writers compute the same stream_version.

Non-constraint SQL and decode errors are still surfaced via the existing error mapping; only qualifying constraint failures trigger the retry.

^{Written by Cursor Bugbot for commit 75247d3. This will update automatically on new commits. Configure here.}

Note

Retry up to 3 times on ConstraintError in makeEventStore.append

Adds an Effect.retry stage in OrchestrationEventStore.ts to handle stream_version race conditions. When an INSERT fails with a SqlError wrapping a ConstraintError, the append is retried up to 3 times before propagating the error.

^{Macroscope summarized 75247d3.}

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