v0.0.32: Keep what builds produce for as long as it is useful

Reports hold the compile output and per-test timings a build was judged on, and
are the only record of what a build did; ninety days threw away the history
worth having. Caches are overwritten rather than accumulated, so fourteen days
bought nothing and cost a full rebuild to any repository built less often than
fortnightly.

The whole bucket is under a gibibyte, at $0.023 a gibibyte-month, so the limits
are now set by what is worth keeping — and configurable for callers who disagree.

The build location is also lowercased: a bucket reports its own as
EUROPE-NORTH2, which Cloud Build does not recognize as a location.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>