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

lib/game/world.ts

@@ -136,6 +136,36 @@ export function generateRing(
   return { systems, edges: ringEdges(systems.length) }
 }
 
+// BFS over jump routes: every system within maxHops of fromId, mapped to its shortest hop count.
+// `edges` may be undirected pairs (WorldState.edges) or double-directed route rows — duplicates are
+// harmless because a visited system is never re-queued. fromId itself is not in the result.
+export function reachableWithin(edges: [number, number][], fromId: number, maxHops: number): Map<number, number> {
+  const adj = new Map<number, number[]>()
+  for (const [a, b] of edges) {
+    if (!adj.has(a)) adj.set(a, [])
+    if (!adj.has(b)) adj.set(b, [])
+    adj.get(a)!.push(b)
+    adj.get(b)!.push(a)
+  }
+  const dist = new Map<number, number>()
+  const seen = new Set([fromId]) // the origin is never re-queued or reported
+  let frontier = [fromId]
+  for (let hop = 1; hop <= maxHops; hop++) {
+    const next: number[] = []
+    for (const id of frontier) {
+      for (const nb of adj.get(id) ?? []) {
+        if (!seen.has(nb)) {
+          seen.add(nb)
+          dist.set(nb, hop)
+          next.push(nb)
+        }
+      }
+    }
+    frontier = next
+  }
+  return dist
+}
+
 // --- Bodies (planets + moons) and exploration -------------------------------
 
 export interface WorldMoon {