…pipeline

Summary:
Intent:
- Stovepipe had a full-stack integration suite but no e2e suite, and nothing proved the asynchronous process stage actually drained a message — the integration suite only asserts that Ingest publishes one.
- Add an e2e suite whose distinguishing charter is proving the ingest→process pipeline runs end-to-end, mirroring the submitqueue test/e2e pattern.

Changes:
- Add test/e2e/stovepipe with a testify suite (suite_test.go) that boots service/stovepipe/docker-compose.yml under the e2e-stovepipe context and a harness (harness_test.go) of intent-level helpers.
- Tests cover Ping, Ingest happy-path (synchronous request/request_uri/queue_messages side effects plus asynchronous consumption), and Ingest idempotency/dedup.
- awaitProcessed observes the durable acked-offset watermark in queue_offsets (which only advances on ack) rather than the message's delivery-state row, because the queue GCs acked messages from queue_messages once the watermark passes them.
- Left the existing integration suite untouched (added alongside, per the submitqueue precedent of keeping both levels).

Test Plan:
- bazel test //test/e2e/stovepipe:stovepipe_test passes (Ping, Ingest happy-path, Ingest idempotency) against the Docker Compose stack. Non-vacuity confirmed: an offset-based signal that is absent makes awaitProcessed time out (observed while iterating), so the async assertion is real.

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