feat(stovepipe): add request logs for dlq outcomes

[mnoah1]

Summary

This PR builds on #666, which records normal request outcomes and lifecycle events.

Intent:

• Retain the terminal reason when an exhausted pipeline stage forces a request to fail.
• Repair a missing failure occurrence when DLQ reconciliation redelivers after the request write.

Changes:

• Record processing_failed for Process and Build DLQ reconciliation.
• Record build_polling_exhausted for BuildSignal DLQ reconciliation.
• Persist the failed request state before its log and preserve all other terminal outcomes.
• Wire the shared request-log materializer into the three DLQ controllers.

Test Plan

• Exercise new failure logging, retry repair, write ordering, stage-specific reasons, and server wiring in Bazel tests.

Revert Plan

• Revert this change to leave DLQ reconciliation state-only.

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AI Verification

Validated at 81789e9 on Sep 9 21:46 UTC · 21 files analyzed · 2s

Validator	Status	Issues
go-coverage	not_applicable	0
ios-test	not_applicable	0
web	not_applicable	0
diff-template	not_applicable	0
android-lint	not_applicable	0
android-coverage	not_applicable	0
uber-one	not_applicable	0
go-thrift-lint	not_applicable	0
java-lint	not_applicable	0
java-coverage	not_applicable	0
ios-lint	not_applicable	0
go-lint	not_applicable	0
go-proto-lint	not_applicable	0
custom	not_applicable	0
ureview	completed	0

0 issues detected

_{Skipped validators: claude · EngWiki}

Issues