#326 B6: retire reconcile/reconstruct paths (Axis B cleanup)

Part of #318 (epic). Axis B — cleanup/retire. Depends on B4 (green) + B5.

Goal

Delete the old reconcile/reconstruct machinery now that the authoritative relocation-bitmap core (B2–B5) fully replaces it.

Delete

• ag-image-canonicalize-heap-keywords (cave#314 reconcile)
• the pass-1/pass-2 per-object rebuild in src/warm/image.lisp
• the pool-slot relocation passes (ag-image-relocate-restored-pool-*)
• ADR 0014's GC-walk serializer in save-image

Acceptance gate

Full suite green incl. asdf load with the old paths GONE (not just unused). build/funcl-asdf boots to asdf-ready in a fraction of a second. Update ADR 0014 (loading half superseded) and ADR 0025 status. Definition-of-done in #318 fully met.