Add ADR-004 storage layer with append-only executions, summary
regeneration, idempotency keys, and retention pruning. Wire memory init
to scaffold .kaizen/metrics/ by default and add unit tests.
Persist INTENT and ecosystem assessments in history/, add ADR-004 for
project metrics with Helix Forge correlation, and register WP-0003 and
WP-0004 workplans with State Hub. Update SCOPE, README, and agency-framework
docs to reflect the two-layer measurement model.
