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/host-api-proxy.test.ts

@@ -40,13 +40,13 @@ describe('Host API IPC proxy', () => {
     expect(fetchHandler).toBeTypeOf('function');
 
     const result = await fetchHandler(undefined, {
-      path: '/api/opencode/projects/create',
+      path: '/api/coding/projects/create',
       method: 'POST',
       body: JSON.stringify({ projectName: '测试项目' }),
     });
 
     expect(fetchMock).toHaveBeenCalledWith(
-      'http://127.0.0.1:13210/api/opencode/projects/create',
+      'http://127.0.0.1:13210/api/coding/projects/create',
       expect.objectContaining({
         method: 'POST',
         headers: expect.objectContaining({