Writable mode: write(key, body) stages and commits the file (skipping a no-op so
no empty commit is created), returning the page at the new commit sha. The
writable profile declares WRITE + VERSION with PER_PAGE granularity. current_rev
is the per-path commit sha, so a write — or an external commit to the same path —
moves it, driving apply-under-drift. Passes the conformance positive-write probe.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
