feat(npcs): drop binding; select NPCs on storyline export

Remove storyline/scene NPC binding and export chosen NPCs with relations/groups. Harden export modal so a missing npcs payload no longer blacks out the editor.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/main/foundry/foundryImport.ts

@@ -18,7 +18,6 @@ import type {
   FoundryPlaylistDoc,
   FoundrySceneDoc,
 } from '../../shared/foundry/foundryTypes';
-import { noneBinding } from '../../shared/npcs/npcBinding';
 import { DEFAULT_NPC_GROUP_COLOR, normalizeHexColor } from '../../shared/npcs/npcGroups';
 import type {
   MediaAsset,
@@ -447,7 +446,6 @@ export async function buildProjectFromFoundryDocuments(
       x: 80 + (npcIndex % 4) * 220,
       y: 80 + Math.floor(npcIndex / 4) * 200,
       groupId,
-      binding: noneBinding(),
     });
     npcIndex += 1;
   }