[Parity]: [P3] Auto-floor bridge distance rule (watch-only, by design)

Imported from the engineering backlog (_bmad-output/implementation-artifacts/backlog.md, story auto-floor-bridge-distance).
Priority P3 (do-first order) | Severity: low | Status: open | Epic: SimTower parity | Type: review-deferral | Recorded: 2026-07-09

Divergence from the 1994 original

Watch-only, by design. From the v1.15.0 auto-floor-build (2) review (gds-code-review, Acceptance Auditor + Edge Case Hunter). Tower.bridgeFillPlan bridges to the nearest same-substrate structure with no maximum-gap cap and scans out to the lot edge. Two linked notes: (a) a distant nearest-neighbor auto-fills (and charges for) a long floor run, and can block an otherwise-affordable module with only a generic "Not enough money." toast; (b) when no neighbor exists on a story, the hover-preview scan runs to the lot edge each frame (bounded, cheap Map.gets, ~2xGRID.width per story, but at hover cadence). Kept nearest-neighbor unbounded because that matches the owner's stated intent ("fill the gap between them") and is pinned by a far-gap test. If the far-gap fill reads as surprising, add a max-gap cap (and a bridge-specific refusal message); if the hover scan ever shows up in a profile, short-circuit when the first column out is empty on both sides.

Start with _bmad-output/implementation-artifacts/backlog.md and the auto-floor-bridge-distance story, then inspect Tower.bridgeFillPlan and the linked far-gap test. The issue is watch-only: completion requires a settled decision about a maximum-gap/refusal behavior or a hover-scan optimization, followed by corresponding tests and review.