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/routes/app.ts

@@ -17,14 +17,13 @@ export async function handleAppRoutes(
     });
     res.write(': connected\n\n');
     ctx.eventBus.addSseClient(res);
-    res.write(`event: opencode:status\ndata: ${JSON.stringify(ctx.opencodeManager.getStatus())}\n\n`);
     return true;
   }
 
   if (url.pathname === '/api/app/runtime-info' && req.method === 'GET') {
     sendJson(res, 200, {
-      runtime: 'opencode',
-      status: ctx.opencodeManager.getStatus(),
+      runtime: 'pi',
+      diagnostics: ctx.codingProducts?.runtime.getDiagnostics() ?? null,
     });
     return true;
   }