TASK-016 review: complete remaining minor cleanup pass

Final pass through the 26 minor items that survived the first cleanup
batch (6e55621). Net result: 47/50 review items resolved across both
batches, 3 explicitly deferred with rationale.

Deferred (left [ ] with *Status:* — distinct from "not addressed"):
- #44 acceptance-criteria: nice-to-have integration test for
  request_completed trampoline (unit-level proxy in test 8 is acceptable).
- #46 redundant-test: tests have distinct traceability value.
- #47 excessive-setup: cosmetic test refactor deferred.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: etr