Executing the Rebuild

Turn the rebuild spec (layer docs + REBUILD-PLAN.md) into actual code in the target stack, and measure how faithfully it carried over. The differentiator: completeness is verified by re-scanning the rebuilt repo and diffing it against the source graph — a before/after picture — not asserted.

Requires: a completed plan — docs/unwind/REBUILD-PLAN.md + docs/unwind/.cache/rebuild-decisions.json + docs/unwind/rebuild-graph.json + docs/unwind/layers/**. (Run uw-plan and uw-graph/uw-dashboard first.) Produces:

• Target-stack code in the chosen target repo (via builder subagents).
• docs/unwind/.cache/rebuild-state.json — the durable rebuild ledger (resume + loop).
• docs/unwind/.cache/rebuild-map/<sliceId>.json — per-slice source→target mappings.
• docs/unwind/.cache/rebuild-progress.json — overlay the dashboard renders.
• docs/unwind/rebuild-verification-graph.json + docs/unwind/rebuild-gaps.md.

Principles: builders follow rebuild-principles.md (functional equivalence, [MUST] inviolable, record every mapping, never silently skip).