[Feature]: [P2] Full 1994 parking-ramp connectivity parity (own story + SAVE_VERSION bump)

Imported from the engineering backlog (_bmad-output/implementation-artifacts/backlog.md, story parking-ramp-connectivity).
Priority P2 (do-first order) | Severity: n/a | Status: idea | Epic: SimTower parity | Type: feature-request | Recorded: 2026-07-07

Problem / motivation

Gated, own story + own SAVE_VERSION bump; do NOT fold into the segment-parity initiative. Full 1994 ramp parity: first ramp under the lobby, ramps vertically stacked, a space works only if its ramp column connects up to the lobby, replaces the per-ramp independent-seed model in functionalParkingSet (Tower.ts:971). Party verdict (Cloud Dragonborn/Samus Shepard/Link Freeman, 2026-07-07): defer. Deciding factor: it's a spatial-regime change that re-evaluates on load, and W1 (transport-too-far) already is one, shipping both in one migration makes the change unattributable to the player. Must-haves if built: (1) migration heals not harms, build the missing ramp column up to the lobby so no existing tower loads with newly-dead parking ("heal or don't touch it"); (2) exactly one spatial-regime change per load, never combine with the W1/W2/W3 rollout; (3) telegraph the repair loudly (one honest toast, never a silent mutation); (4) no split-brain legacy-seed flag in functionalParkingSet, connectivity applies to all towers once shipped, which is why the healing migration is mandatory. Design merits are sound (more faithful, more strategic depth); this is purely a sequencing/legibility deferral.

Start with the parking logic at Tower.ts:971, the functionalParkingSet per-ramp seed model, and the SAVE_VERSION migration path. Define the load-time healing migration so ramp columns connect to the lobby, emit one honest toast, avoid combining with W1/W2/W3, and apply connectivity to all towers without a legacy-seed flag.