The tier_aware_ratio_enabled path (#928) binned SOLD deals by sold-ppm² against
ASKING-derived percentile bounds, then divided within-tier medians. That is a
ratio-of-truncated-medians ARTIFACT: a Monte-Carlo with a CONSTANT true
sold/asking=0.84 reproduced the prod tier values (0.94/0.99/0.96) and the skewed
deal split (57/27/15%) exactly — the "premium sells closer to asking" gradient is
100% spurious. Flipping the flag ON made prod WORSE (overall MAPE 14.6→17.2,
эконом bias +5.8→+18.1). It shipped dark (default False) but is a latent footgun.
A valid within-price-tier sold/asking is uncomputable from asking-less ДКП deals;
the per-rooms blend + the shipped hedonic (year+area) are the correct conditioning.
So the dead path is removed entirely, not just disabled.
- estimator._get_asking_sold_ratio: drop the tier branch (bounds read, t33/t66,
asking_to_sold_ratios_tiered read, empirical-Bayes shrink) + the _legacy/tier
cache-key split; keep only the legacy per-rooms → global -1 lookup. Cache key
collapses to rooms bucket. anchor_ppm2 param retained for call-site compat (now
unused).
- config: remove tier_aware_ratio_enabled + tier_ratio_shrink_k settings.
- tasks/asking_to_sold_ratio: drop the tiered refresh (DELETE/re-derive bounds +
tier rows, tiered counters); the daily task no longer touches the dead tier
tables. Legacy asking_to_sold_ratios DELETE+re-derive intact.
- tests: delete the tier-ratio unit test file (legacy path covered by
test_estimator_expected_sold.py Layer 1); fix the daily-refresh fake-db
(8→3 execute calls, 3 counter keys); drop the two segment-guard tests that
asserted the removed tiered SQL; clean a dead per_rooms_tier basis in fixtures.
Tier tables asking_to_sold_ratios_tiered / asking_to_sold_tier_bounds + migration
098 are left in place (inert once nothing reads/writes them); a DROP migration is
a separate, optional follow-up.
Regression gate stays byte-identical (flag was False in prod → active path
unchanged). Refs #2002
