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/context.ts

@@ -1,6 +1,5 @@
 import type { BrowserWindow } from 'electron';
-import type { OpencodeManager } from '../opencode/manager';
-import type { OpencodeProjectStore } from '../opencode/project-store';
+import type { CodingProjectStore } from '../coding-projects/project-store';
 import type { HostEventBus } from './event-bus';
 import type { createWorksSubmissionBindingStore } from '../services/works-submission-binding';
 import type { DesignWorkspaceModule } from '../image-workspace/module';
@@ -69,8 +68,7 @@ export interface AgentBrowserService {
 }
 
 export interface HostApiContext {
-  opencodeManager: OpencodeManager;
-  opencodeProjectStore: OpencodeProjectStore;
+  codingProjectStore: CodingProjectStore;
   eventBus: HostEventBus;
   mainWindow: BrowserWindow | null;
   agentBrowser?: AgentBrowserService;