feat: remove legacy OpenCode runtime

Cut product flows over to Coding/Pi and retain only the migration-owned v1 boundary. Promote supported native optional packages because electron-builder omitted pnpm transitive optional closure from the packaged ASAR.

shared/coding-product-tools.ts

@@ -57,6 +57,9 @@ export interface ProductCodingSkill {
   name: string;
   description: string;
   selected: boolean;
+  location: string;
+  content: string;
+  entries: Array<{ path: string; type: 'file' | 'directory' }>;
 }
 
 export interface ProductCodingCommand {