test: add Sqrzl-backed qualification coverage for partitioned compaction (gap from #270)

[smiggleworth]

Summary

Issue #270 (bound compaction memory and partition SST outputs) requires cloud qualification coverage across local, simulated-cloud, and Sqrzl-backed environments for multi-output compaction upload/publication/recovery:

Local, simulated-cloud, and Sqrzl-backed cloud qualification cover multi-output upload/publication/recovery. Cloud readers never observe a partially mirrored replacement set as authoritative.

Local and simulated-cloud coverage exist and pass (e.g. should_preserve_partitioned_compaction_across_local_reopen / ..._simulated_cloud_reopen in src/engine/tests.rs, and the partial-upload rollback test in tests/failure_injection.rs). No equivalent exists against real Sqrzl.

This is not a report that the simulated-cloud emulator is misbehaving — the emulator-backed tests pass. The gap is that a Sqrzl-backed test for this scenario doesn't exist at all, not even as #[ignore]d code pending a scheduled/manual run.

Current state

tests/cloud_provider_engine_qualification.rs (feature-gated cloud-all,sqrzl-tests) contains Sqrzl-backed tests, but they only cover generic "recover engine from provider after local cache loss." None of them is compaction- or partition-specific, and there's no evidence any Sqrzl run has exercised the bounded/partitioned compaction path from #270.

Requirement

Add a Sqrzl-backed qualification test (may be #[ignore]d, gated to run in the scheduled/manual Cloud Qualification workflow per existing convention) that:

• Compacts input SSTs into multiple output partitions against a real Sqrzl-backed store.
• Verifies multi-output upload, manifest publication, and recovery.
• Includes a failure-injection variant analogous to should_rollback_partition_set_after_partial_remote_compaction_upload (currently simulated-cloud only) so a partial-upload/publish failure against real Sqrzl is proven to never leave a partially-mirrored replacement set authoritative.

Acceptance criteria

• A Sqrzl-backed test exercises multi-output compaction upload/publication/recovery, analogous to the existing simulated-cloud coverage.
• A Sqrzl-backed failure-injection test proves a partially mirrored replacement set is never observed as authoritative.
• Tests are wired into the scheduled/manual Cloud Qualification workflow, consistent with other sqrzl-tests-gated tests.
• Issue perf: bound compaction memory and partition SST outputs #270's acceptance criterion "Local, simulated-cloud, and Sqrzl-backed cloud qualification cover multi-output upload/publication/recovery" can be marked satisfied.

Context

Found during an audit of #270's acceptance criteria against PR #271 (branch perf/270-bounded-compaction).

[smiggleworth]

Completed by #277 and verified after squash merge. Both requested Sqrzl-backed regressions—should_recover_partitioned_compaction_from_sqrzl_s3_after_local_cache_loss and should_rollback_partition_set_after_partial_sqrzl_compaction_upload—run in the scheduled/manual Cloud Qualification provider target.

Exact-main evidence for e8bcbad6fa8e1daedd9bcb5fd8bf7b1b622e2b5d: Cloud Qualification 33894099544 passed the Sqrzl qualification, provider-engine qualification, and full suite. CI 33894068970, Repository Qualification 33894069060, Docker Qualification 33894096213, Platform 33894403243, and Compatibility 33894403315 are also green. The issue is closed as completed.