## Summary
Adds `EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED` (default off), which
makes the task-event store skip all PostgreSQL `TaskEvent` writes. It's
for deployments that store task events in ClickHouse
(`EVENT_REPOSITORY_DEFAULT_STORE=clickhouse_v2`) and no longer want the
PostgreSQL copy.
## How it works
The guard sits at the single postgres write boundary,
`TaskEventStore.create` / `createMany`, so it covers every write path
(OTLP ingestion and run-lifecycle events) with one check. Reads are
untouched (`findMany` / trace queries / streaming), so existing
PostgreSQL events remain readable.
Leave it off unless the default store is `clickhouse_v2`, otherwise task
events for any run still routed to PostgreSQL would be dropped.
Eric Allam
29598a77b8