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.

electron/api/route-handlers.ts

@@ -4,7 +4,6 @@ import { handleAiProxyRoutes } from './routes/ai-proxy';
 import { handleAiHardwareRoutes } from './routes/ai-hardware';
 import { handleAppRoutes } from './routes/app';
 import { handleAuthRoutes } from './routes/auth';
-import { handleOpencodeRoutes } from './routes/opencode';
 import { handleImageWorkspaceRoutes } from './routes/image-workspace';
 import { handleImagePromptMuseumRoutes } from './routes/image-prompt-museum';
 import { handleLearningRoutes } from './routes/learning';
@@ -50,7 +49,6 @@ export const hostApiRouteHandlers: readonly HostApiRouteHandler[] = [
   handleCodingProjectRoutes,
   handleCodingConversationRoutes,
   handleCodingFileRoutes,
-  handleOpencodeRoutes,
   handleSettingsRoutes,
   handleProviderRoutes,
   handleFileRoutes,