fix: stop orphaned opencode processes on desktop quit

Exit the desktop app without waiting on background cleanup
Kill managed OpenCode by process group with a port fallback
Make OpenCode shutdown reuse the active shutdown promise

packages/web/server/lib/opencode/shutdown-runtime.js

@@ -29,7 +29,9 @@ export const createGracefulShutdownRuntime = (dependencies) => {
     tunnelAuthController,
   } = dependencies;
 
-  const gracefulShutdown = async (options = {}) => {
+  let shutdownPromise = null;
+
+  const runShutdown = async (options = {}) => {
     if (getIsShuttingDown()) return;
 
     setIsShuttingDown(true);
@@ -133,6 +135,12 @@ export const createGracefulShutdownRuntime = (dependencies) => {
     }
   };
 
+  const gracefulShutdown = (options = {}) => {
+    if (shutdownPromise) return shutdownPromise;
+    shutdownPromise = runShutdown(options);
+    return shutdownPromise;
+  };
+
   return {
     gracefulShutdown,
   };