[P2] consumer-prices: movers feed publishes parse artifacts (+874% sugar, -99% bread, 1-item retailer baskets) — blocks publishing shelf-price receipts

Live get_consumer_prices (ae) pull on 2026-07-22: topMovers contains obviously wrong deltas — White Sugar 1kg +874.68% (lulu_ae), Whole Chicken +608.86% (spinneys_ae), Yaumi bread -99.25% — consistent with unit/pack-size confusion or price-parse drift; retailer-spread basket itemCount=1 per retailer and headline spreadPct=0 while per-retailer totals differ 0-352%; overview wowPct/momPct all 0 while movers show huge swings (aggregate and movers disagree). Blog post ground-truth-inflation-shelf-price-tracking cannot print receipts until movers are trustworthy; found during the blog receipts round.

Start by reproducing the live get_consumer_prices (ae) pull and compare topMovers with the retailer-spread basket and overview aggregates. Trace the price parsing and aggregation entry points exposed by that pull; done means movers, item counts, spread percentages, and overview changes agree with the retailer totals well enough to publish shelf-price receipts.

Written by the indexing model from the issue text.