ZoningType gains PartialOrd/Ord (DistrictType T-994 mirror) for the
dominant_zoning declaration-order tie-break. layer_proxy:
QuarterFootprintEntry/QuarterFootprintLayer (BTreeMap keyed by
city_id; density_avg_pct floor-mean, dominant_* mode with
declaration-order tie-break, landmark/corridor counts) +
build_quarter_footprint_layer gated None on empty state.quarters;
sixth AtlasLayerResponse field wired into all construction sites;
growth-ceiling doc updated to say the whole-body budget is consumed
(what carries a seventh is T-1124's design, resolved in the same
branch's amendment). Placements whose derived Layer4Quarter id is not
yet in state.quarters are SKIPPED (skeleton gen is async Low-priority
— entries may be a proper subset; client decodes defensively). Stale
TODO(#957) removed (premise predates T-957 landing).
Tie-break bug caught by its own test: Iterator::max_by_key over a
BTreeMap returns the LAST max on ties — backwards from
declaration-order-first; replaced with an explicit forward walk that
replaces only on strictly-greater count.
gen_fixtures: populated RegionGridLayer (T-1118 replay coverage) +
QuarterFootprintLayer literals in the ready fixture; msgpack fixtures
regenerated via make fixtures. Note: landmark_count is inert on real
data today (BlockSkeleton.landmark hardcoded None until landmark
placement lands); fixtures use non-zero counts to exercise the logic.
5 new unit tests + populated round-trip; atlas:: 549 green.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
jpmschweitzerandClaude Fable 5
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