[Feature]: [P3] Gate the commercial demand pool by open hours (time-gated venues earn a diluted share)

Deferred from the Nightclub review (v1.91.0, PR for the modern-nightclub branch).

computeDemandMap sums EVERY operational footfall venue's capacity into totalCap with no isOpenAt gate, and each venue earns min(1, pool / totalCap) of its daily figure. So a time-gated venue is diluted by venues that are closed at that hour, and it dilutes them when it is closed.

This is a pre-existing property of the demand model (a restaurant already dilutes fast food at breakfast), but the Nightclub is the extreme non-overlap case: at 1am it is often the only open venue, yet it still shares the pool with every closed daytime shop/food hall/boutique, so it captures only a capacity-proportional slice of its 10,000/day headline while paying a 40,000/month DJ booking plus overhead. It may be economically nonviable in exactly the retail-heavy towers where a player would build it, which undercuts the "night inversion" the GDD calls for.

Fix options:

• Gate totalCap (and the per-unit share) on isOpenAt(kind, hour), so only venues open at that hour compete for that hour's pool. This is a demand-model change affecting ALL footfall venues, so it needs a golden-master re-pin and a determinism check.
• Or interim: tune the Nightclub's dailyTrafficIncome up to compensate (a band-aid; the model limitation stays for every time-gated venue).

Source: Nightclub /gds-code-review defer (Edge Case Hunter). The Nightclub itself ships correct; this is a balance/model refinement for time-gated venues generally.

Start by locating computeDemandMap and the isOpenAt logic, then review the demand model's golden-master fixtures and determinism check. Confirm the intended model-level approach for all footfall venues; done means the hourly pool and per-unit share account for venues open at that hour, with the golden master re-pinned and determinism preserved.