ADR-0010: Offline-ready invariants, build online-first

Status: accepted (carried; validated by the LLD — offline is a device branch — and the data plane’s precompiled offline read path)

We build online-first, but four kernel invariants are non-negotiable from day one because they are expensive to retrofit: coarse semantic Actions; client-minted IDs with idempotency keys; expected-version writes; evidence captured with the write. Offline is then a device branch — the same branch mechanics, the same pipeline with the first two query stages precompiled — not a second architecture. The offline client stack itself is deferred.