Go's test-result cache sits below the Docker layer cache that issue #26
addresses. CHECK_EPOCH forces the RUN make test step to re-execute, but
GOCACHE baked into earlier image layers survives into the re-executed
step, so go test can still do no work. Record that these are two
separate defects so a fix for one is not recorded as covering the other.
Also correct the TODO.md Completed Steps date to the landing date, which
matches the REPO_POLICIES.md last_modified front matter.
Closes#44
