Issue #10 Task 5, the acceptance claim. Before the fix this asserted
against 'qwen_1 请求被拒: 400' and failed on the first substring - which
is exactly what the downstream batch was left with. Uses the real body
from the issue, and checks the trailing code too, since a head-only cut
would drop the one field you quote when chasing the provider.
Classify empty completions as transient per human ruling (fixes flaky
real-gateway smoke and prevents caching empty responses), rename the
factory injection parameter gate to breaker per the frozen design,
rewrite the probe-entry cleanup without except BaseException, declare
python-dotenv explicitly, add a mid-backoff cancellation test, and
record all implementation errata in the design and architecture docs.