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.
Also note that the seven architecture amendments predate the plan,
tighten T12 to independent implementation layers, and add fallback
guidance for read-only reference protocol imports.
iomgaa