Fix npx permission issue in Stdio transport by injecting /tmp fallbacks

src/lib/ai/mcp/create-mcp-client.ts

@@ -212,11 +212,19 @@ export class MCPClient {
         }
 
         const config = MCPStdioConfigZodSchema.parse(this.serverConfig);
+        
+        // Inject writeable fallback directories for restricted container users (e.g. npx cache permissions)
+        const fallbackEnv: Record<string, string> = {
+          HOME: "/tmp",
+          npm_config_cache: "/tmp/.npm",
+          XDG_CACHE_HOME: "/tmp/.cache",
+        };
+
         this.transport = new StdioClientTransport({
           command: config.command,
           args: config.args,
-          // Merge process.env with config.env, ensuring PATH is preserved and filtering out undefined values
-          env: Object.entries({ ...process.env, ...config.env }).reduce(
+          // Merge process.env with fallbackEnv and config.env, ensuring PATH is preserved and filtering out undefined values
+          env: Object.entries({ ...process.env, ...fallbackEnv, ...config.env }).reduce(
             (acc, [key, value]) => {
               if (value !== undefined) {
                 acc[key] = value;