[Parity]: [P3] Star-tiered lobby fees (new mechanic, gated)

New mechanic (design gated, provisional): star-tiered lobby fees, spun out of #573.

The 1994 game charges lobby upkeep tiered by star rating: free at 1-2 stars, 300 per lobby segment at 3 stars, 1,000 per segment at 4+ stars. The engine models no lobby fee today (Classic lobbies are free forever), so this is a new mechanic, not a maintenance-chart row.

Design authored in _bmad-output/planning-artifacts/design/gdd-star-tiered-lobby-fees-2026-07-22.md. Implementation is gated on #575-grade primary verification of the fee figures AND the "segment" definition (per tile vs per placed lobby unit vs canon span), both single-lineage today (BStuart FAQ -> Relentless Optimizer -> Fandom, not independent; the official manual is silent). Open questions: segment definition, whether sky lobbies each incur the fee, star-boundary re-read timing, and the Modern stance (free/canon/custom).

Route through a GameRules.lobbyFeePerSegment(star) seam so Modern stays byte-identical until deliberately changed. /gds-code-review + version bump on implementation.

Start with _bmad-output/planning-artifacts/design/gdd-star-tiered-lobby-fees-2026-07-22.md and the primary verification required by #575. Resolve the segment definition, sky-lobby behavior, star-boundary timing, and Modern stance before implementation. If approved, route the mechanic through GameRules.lobbyFeePerSegment(star), preserve Modern byte-identical behavior, and follow /gds-code-review plus the version bump.