feat(npcs): inspect cards, Show overlay, and optional external link

Clicking an NPC tile opens description cards (multi-select accordion); Show puts avatars on screen. Optional URL opens a webview tab. Avatar pan in the editor commits on pointer up.

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

app/shared/ipc/contracts.ts

@@ -443,6 +443,7 @@ export type IpcInvokeMap = {
       npcId?: NpcId;
       name: string;
       description?: string;
+      externalUrl?: string;
       filePath?: string;
       groupId?: NpcGroupId | null;
       ringColor?: string;
@@ -457,6 +458,7 @@ export type IpcInvokeMap = {
       npcId: NpcId;
       name?: string;
       description?: string;
+      externalUrl?: string;
       groupId?: NpcGroupId | null;
       ringColor?: string;
       disposition?: NpcDisposition;