Q123: files shared in a private conversation stay with its members

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/shared/commands/files.ts

@@ -1,5 +1,7 @@
 export interface ImportFileInput {
   orgId: string;
+  /** The conversation the file is attached in; a direct or restricted one keeps the file to its members. */
+  spaceId?: string;
 }
 
 export interface OpenFileInput {