Addresses PR #167 review (Tyre T1, T3).
T1 — the region climate tier was built but no live path consulted it: both
derive_district_profile (cascade) and derive_district (on-demand) passed
region_baseline_c: None, so the D-243 §4 edge-fuzz blend was dead in production
and district temperature was still derived from scratch. Now both paths compute
region_baseline_at_district(...) and pass it through build_district_profile so
the two-phase modulation (D-243 §3) actually runs. The cascade path
(derive_all_districts) builds a BTreeMap<RegionPos, RegionProfile> covering all
district positions + their +/-1 neighbours once per body and looks up from it;
the on-demand path derives the four surrounding region baselines on the fly.
No production path passes None except genuinely airless bodies (no planet_class).
T3 — renamed BodyParams.district_latitude_deg -> latitude_deg (it is the region
centre latitude in the region fns, a call-site trap under the old name);
dual-scale doc; propagated to body_params_reader.rs and all literal sites.
Golden fixtures are unaffected (they construct districts directly via make_region,
bypassing build_district_profile) — derivation_harness 37/37 green, no re-pin.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.8
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