feat(event-router): E2E integration tests for event-triggered saga dispatch (#1377)

* feat(event-router): add E2E integration tests for event-triggered saga dispatch

Add comprehensive integration tests verifying the full event-to-saga
dispatch flow using testcontainers (CockroachDB + Kafka). Tests cover:

- Happy path: event matching CEL filter triggers correct saga
- Filter rejection: non-matching events silently skipped
- Metadata filtering: CEL filters on metadata fields
- Idempotency: duplicate events with same correlation ID deduplicated
- Chain depth enforcement: events exceeding max depth dropped
- Multi-saga dispatch: multiple sagas on same channel with different filters
- E2E Kafka: publish to Kafka topic, consume, evaluate filters, trigger sagas

* fix: address PR review comments for integration tests

- Log errors in consumeAndDispatch instead of silently discarding them
- Add explanatory comment for the idempotency wait-then-timeout pattern

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Co-authored-by: Ben Coombs <bjcoombs@users.noreply.github.com>

Author: bjcoombs