feat(game): NAVIGATION AI unlocks two-hop jumps in one action (#35)

lib/game/save.ts

@@ -6,7 +6,7 @@ import { generateStartingCrew, rollCrewMember, startingCrewRng, type CrewMember
 import { BASE_CAPACITY, BASE_LEVEL, SHIP_TYPES } from './ship-costs'
 import { checkMissionCompletion, topUpMissionBoard } from './missions'
 import { TECHS } from './tech'
-import { bodyRng, explorationRng, generatePlanets, generateRing, generateStartRegion, mulberry32, rollExploration, type FoundItem } from './world'
+import { bodyRng, explorationRng, generatePlanets, generateRing, generateStartRegion, mulberry32, reachableWithin, rollExploration, type FoundItem } from './world'
 
 // Save lifecycle: auto-init on first hit, world state reads, and the jump action.
 // Single-player by design — exactly one save row ever exists, so every query below is
@@ -217,10 +217,13 @@ export async function jumpToSystem(db: GameDb, systemId: number): Promise<WorldS
   if (current.id === target.id) throw new JumpError(409, 'Already at this system')
 
   const routes = await db.db.select().from(schema.jumpRoutes)
-  const adjacent = routes.some((r) => r.fromSystem === current.id && r.toSystem === target.id)
-  if (!adjacent) throw new JumpError(409, `${target.name} is not reachable from ${current.name}`)
+  // #35 — NAVIGATION AI extends the jump range from adjacent (1 hop) to 2 hops; a multi-hop jump
+  // costs one turn per hop, so single-hop jumps keep their existing cost.
+  const navAi = (await db.db.select().from(schema.tech)).some((t) => t.slug === 'NAV_AI' && t.researched)
+  const hopCount = reachableWithin(routes.map((r) => [r.fromSystem, r.toSystem]), current.id, navAi ? 2 : 1).get(target.id)
+  if (hopCount === undefined) throw new JumpError(409, `${target.name} is not reachable from ${current.name}`)
 
-  const turn = save.turn + 1
+  const turn = save.turn + hopCount
   await db.db.update(schema.solarSystems).set({ isCurrent: false }).where(eq(schema.solarSystems.id, current.id))
   await db.db.update(schema.solarSystems).set({ isCurrent: true, discovered: true }).where(eq(schema.solarSystems.id, target.id))