### CI: a full runner disk fails a byte-equality leg as infrastructure, not as a divergence

- **CI:** each leg of the two cross-architecture byte-equality matrices (`wai-byte-equality.yml`, and
  `wai-conformance.yml`'s `byte-exact`) measures the free space under its workspace, the runner's temporary directory,
  TMPDIR and HOME before the checkout, and writes and syncs 32 MiB on each filesystem. Below 4 GiB, or on a write
  refused for space, an I/O error or a read-only filesystem, the leg fails in a step named for infrastructure, with an
  error that says no fixture was decoded. When a later step fails, the measurement and the write are made again, and
  the failure is named infrastructure if the disk filled meanwhile.

