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/models-page.test.tsx

@@ -5,19 +5,12 @@ import { Models } from '@/pages/Models/index';
 const hostApiFetchMock = vi.fn();
 const trackUiEventMock = vi.fn();
 
-const { opencodeState, settingsState } = vi.hoisted(() => ({
-  opencodeState: {
-    status: { state: 'running', port: 4096, url: 'http://127.0.0.1:4096', startedAt: 1, pid: 1234 },
-  },
+const { settingsState } = vi.hoisted(() => ({
   settingsState: {
     devModeUnlocked: false,
   },
 }));
 
-vi.mock('@/stores/opencode', () => ({
-  useOpencodeStore: (selector: (state: typeof opencodeState) => unknown) => selector(opencodeState),
-}));
-
 vi.mock('@/stores/settings', () => ({
   useSettingsStore: (selector: (state: typeof settingsState) => unknown) => selector(settingsState),
 }));
@@ -38,10 +31,6 @@ vi.mock('@/components/common/FeedbackState', () => ({
   FeedbackState: ({ title }: { title: string }) => <div>{title}</div>,
 }));
 
-vi.mock('@/pages/Models/OpencodeRuntimePanel', () => ({
-  OpencodeRuntimePanel: () => null,
-}));
-
 vi.mock('react-i18next', () => ({
   useTranslation: () => ({
     t: (key: string, fallback?: string | { count?: number }) => {
@@ -70,7 +59,6 @@ describe('Models page auto refresh', () => {
   beforeEach(() => {
     vi.useFakeTimers();
     vi.clearAllMocks();
-    opencodeState.status = { state: 'running', port: 4096, url: 'http://127.0.0.1:4096', startedAt: 1, pid: 1234 };
     Object.defineProperty(document, 'visibilityState', {
       configurable: true,
       value: 'visible',