fix: unblock #1575 Integration (media-buy) batch tally assertion

[mkostromin-sigma]

Parent

Parent: #1606 (umbrella). Also unblocks #1575 merge.

Blocking

Blocks #1636 (schema/outbox leaf).

Problem

PR #1575 CI fails Integration (media-buy) on:
tests/integration/test_delivery_poll_behavioral.py::TestBatchContinuesPastFailedSend::test_failed_send_does_not_abort_batch

Assertion: expected the batch-complete tally in the log; got: ''

Mock proves both buys were attempted (mb_fail, mb_ok), so the batch loop ran. Empty caplog.text indicates log capture flake (CI logging/logfire), not missing tally logic.

Fix direction

• Make _send_reports() return (reports_sent, errors) and assert on the return value instead of (or in addition to) caplog.
• Do not push into fix: media buy delivery correctness — scheduler serving statuses + webhook-only fields #1575 author's branch from our fork — apply via author PR review / author commit, or tiny follow-up after fix: media buy delivery correctness — scheduler serving statuses + webhook-only fields #1575 merges.

Coordination

Review comment left on #1575

Out of scope

Durable outbox / sequence reservation (#1606 L1+).

[mkostromin-sigma]

Status

Suggested fix implemented on our branch feat/1606-durable-webhook-outbox (not pushed into #1575):

• _send_reports() returns (reports_sent, errors)
• TestBatchContinuesPastFailedSend asserts on the return value (no fragile caplog)

Constraint: we will not push into the #1575 author branch. Please either cherry-pick the tally-return change into #1575, or we land it after #1575 merges as part of #1635 / outbox PRs.

Comment already on PR: #1575 (comment)

[mkostromin-sigma]

Update after #1575 head 1f115921: author already pinned batch continuation via send-count and deferred the return-value tally to this issue. Our branch feat/1606-durable-webhook-outbox (rebased onto latest #1575) implements _send_reports() -> (reports_sent, errors) and asserts (1, 1) in TestBatchContinuesPastFailedSend. Still will not push into the #1575 author branch.

[mkostromin-sigma]

Status

Still blocked on #1575 merge (PR is APPROVED + green + CLEAN as of 2026-07-16). Fix already implemented on feat/1606-durable-webhook-outbox; will land as part of outbox tranche after #1575, not by pushing into the author branch.

Project status set to Blocked.