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.

tests/unit/main-layout-module-gate.test.tsx

@@ -2,7 +2,7 @@ import { render, screen } from '@testing-library/react';
 import { MemoryRouter, Route, Routes } from 'react-router-dom';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import { MainLayout } from '@/components/layout/MainLayout';
-import { useOpencodeStore } from '@/stores/opencode';
+import { codingWorkspaceStore } from '@/stores/coding-workspace';
 import { useProjectConfigStore } from '@/stores/project-config';
 import { useSettingsStore } from '@/stores/settings';
 import { createProjectConfig } from '../../shared/project-config';
@@ -54,7 +54,7 @@ describe('MainLayout module isolation', () => {
       updatedAt: '',
       lastOpenedAt: '',
     };
-    useOpencodeStore.setState({ activeProject: project });
+    codingWorkspaceStore.setState({ activeProject: project });
     useProjectConfigStore.setState({
       configsByProjectId: {
         [project.id]: { ...createProjectConfig(), initialized: false },
@@ -99,14 +99,14 @@ describe('MainLayout module isolation', () => {
   });
 
   it('keeps the local project initialization gate for AI programming routes', () => {
-    renderLayout('/opencode-chat');
+    renderLayout('/chat');
 
     expect(screen.getByTestId('project-initialization-gate')).toBeVisible();
     expect(screen.getByTestId('titlebar-stub')).toHaveAttribute('data-overlay', 'false');
   });
 
   it('keeps the programming workspace padding compensation separate from painting', () => {
-    renderLayout('/opencode-chat');
+    renderLayout('/chat');
 
     expect(screen.getByTestId('main-content')).toHaveClass('basis-0', 'overflow-hidden', 'p-0', 'sm:p-6');
   });