Latency Lab v3.0.3

Release notes

A documentation pass, nothing behavioural

No code path changed in this release. The tracked documentation was read
against the current source and corrected where it had drifted: the README's
stack table now describes the legacy NumPy engine as what it is, the live
execution path for schema_version: 1 models as well as the frozen oracle the
snapshot test pins, rather than "only" an oracle; ARCHITECTURE.md picked up a
punctuation correction. The GitHub Pages site was restamped from VERSION. The
application binaries are unchanged apart from the version they report.