Why: Async notice-run delivery raced with test teardown and in-flight
conversation runs (database closed / material lifecycle flakes).
Evidence: go test ./internal/runmgr/ -run Material
Impact: Reminders append as system messages only; material path still
inlines into startNoticeRun.
Refs: Dev PR #425 CI test-pg failure
Co-authored-by: Cursor <cursoragent@cursor.com>