The financial-uplift model per ADR-0018. `estimate_valuation_uplift(
current_band, target_band, current_value=None, total_cost=None)` returns
a `ValuationUplift`: band-transition uplift compounded from four broker
tables (MoneySupermarket / Lloyds per-step, Knight Frank / Rightmove
whole-jump), taking min/max/mean across the covering sources. Always a
percentage; absolute £ forms (increase at each bound + post-retrofit
value) only when a current market value is supplied; the 2x ROI cap
rescales the percentages and can only bite once a value is known. A
non-improving jump is a clean 0% no-op.
Pure function, no external dependency. Persisting it (where the value
lands) and sourcing the current market value stay deferred (ADR-0018).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
