[Feature]: [P1] Attendance venues are invisible to retail coverage, so an entertainment-led tower can shed tenants past one token shop

Filed from the #548 demand-calibration design party (2026-07-29); the calibration makes this reachable, so it graduates from a footnote to its own row.

Coverage for the unmet-local-demand drain reads only the RETAIL pool (shop, fast food, restaurant and kin): reachableVenuesByOrigin and retailVenueCount both exclude attendance venues (cinema, party hall) by design (#424, they earn from live fill, not the demand pool). Before #548 this was harmless because the eviction region only opened at coverage ~0.02. After the calibration (erosion 0.12, evict floor 0.35, net shed below coverage ~0.20) a tower with one token shop and several thriving cinemas reads its coverage off the shop alone, can sit 10x-20x oversubscribed on paper, and genuinely sheds tenants while running a packed entertainment floor. The zero-retail exemption does not save it: retailVenueCount is 1, so the drain is armed.

The design question (deliberately NOT rushed into the calibration PR): should attendance capacity count toward coverage, and if so how, given that adding it to the coverage denominator without adding it to the income pool breaks the share identity (coverage = min(1, 1/share)), and the 1994 "not enough amenities" evaluation read commerce. Options sketched in the party: a separate attendance-coverage term folded into unmetCoverage, an attendance-aware exemption tier, or ruling that entertainment deliberately does not feed residents and the copy should say so. Chained to the same telemetry gate as the #548 perCapita retune so the ruling is made against real tower data.

/gds-code-review when picked up.

Start with reachableVenuesByOrigin and retailVenueCount, then read the linked #548 calibration and #424 rationale. Use the telemetry gate and real tower data to compare the attendance-coverage options; done means the project has a decided rule, consistent coverage/share semantics, and updated resident-facing copy where required.