Overlay value type (id, target, base_rev, body, state) recorded as an
OVERLAY_CREATED decision-log event (coordination-canonical); get()/open_overlays()
reconstruct from the fold. 4 tests green, pyflakes clean. (ADR-05, blueprint §8.2)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>