Record the first transport failure before SDK teardown, then capture terminal stderr after owned retirement. Preserve exact opaque cancellation reasons and keep foreign cleanup ownership separate through retries.
Validation: 119 focused tests across eight files; five selected baseline regressions; check:fast, docs:check, test discovery; nine real CLI and nine real MCP tiny-APK inspections. Native Windows/Linux startup failures and actual JVM OOM remain unverified.
Closes#4844