feat(ui): render WORLD MAP as a force-directed d3 graph with pan + zoom (#28)

lib/db/schema.ts

@@ -20,7 +20,7 @@ export const solarSystems = sqliteTable('solar_systems', {
   id: integer('id').primaryKey({ autoIncrement: true }),
   saveId: integer('save_id').notNull().references(() => saves.id),
   name: text('name').notNull(),
-  // 0–100 coordinate space, rendered directly by the NodeGraph component.
+  // 0–100 coordinate space; seeds the force-directed WORLD MAP layout (components/world-map.tsx).
   x: real('x').notNull(),
   y: real('y').notNull(),
   discovered: integer('discovered', { mode: 'boolean' }).notNull().default(false),

lib/game/world.ts

@@ -3,7 +3,7 @@
 
 export interface WorldSystem {
   name: string
-  x: number // 0–100 coordinate space, rendered directly by NodeGraph
+  x: number // 0–100 coordinate space; seeds the force-directed WORLD MAP layout
   y: number
 }