test(e2e): cover SubmitQueue DLQ reconciliation

[sbalabanov]

Summary

Intent:

• Ensure an unexpected pipeline failure converges through the real dead-letter path instead of stranding a request.

Changes:

• Drive the dedicated failing conflict analyzer through dependency-analysis dead-lettering.
• Verify the DLQ reconciler fails the batch and request and exposes failure context through request history.

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Test Plan

Issues

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