Build crew gc and clear the backlog
All four §2 deliverables. The backlog clearance runs only after the GC's dry-run report has been reviewed — several worktrees may hold unintegrated work, and live runs from other sessions must never be touched.
/reckon-ship crew-workspace-hygiene
done - no followup. All four §2 deliverables demonstrated: crew gc dry-run-first with disjoint classification, live-pointer refusal on every removal path (gc and cleanup-session), root nesting guard plus removal of the nested root, and a one-line vendored-script dispatch error (commit 039dfaa, 113 tests green). Backlog reviewed then cleared: 5 trees / 2.563 GiB reclaimed with 0 integrated candidates remaining; the 17 unintegrated nova trees (~94 GiB) are peer-owned work gc correctly refuses, and run-directory retention finds 0 candidates because the fleet is younger than the 30-day window. Evidence: docs/evidence/archive/crew-workspace-hygiene-landed.html.