Fix socket error handling to prevent server crashes on ECONNREFUSED

This commit addresses critical issues where unhandled socket connection errors (ECONNREFUSED) would crash the server and cause memory leaks with rising connection counts.

Changes:
- Add createSocketWithErrorHandler() utility that attaches error handlers immediately upon socket creation
- Update https-passthrough-handler to use safe socket creation and clean up client sockets on server connection failure
- Update https-terminate-to-http-handler to use safe socket creation
- Ensure proper connection cleanup when server connections fail
- Document the fix in readme.hints.md and create implementation plan in readme.plan.md

The fix prevents race conditions where sockets could emit errors before handlers were attached, and ensures failed connections are properly cleaned up to prevent memory leaks.

ts/core/utils/socket-utils.ts

@@ -6,6 +6,14 @@ export interface CleanupOptions {
   gracePeriod?: number;     // Ms to wait before force close
 }
 
+export interface SafeSocketOptions {
+  port: number;
+  host: string;
+  onError?: (error: Error) => void;
+  onConnect?: () => void;
+  timeout?: number;
+}
+
 /**
  * Safely cleanup a socket by removing all listeners and destroying it
  * @param socket The socket to cleanup
@@ -197,4 +205,39 @@ export function pipeSockets(
 ): void {
   socket1.pipe(socket2);
   socket2.pipe(socket1);
+}
+
+/**
+ * Create a socket with immediate error handling to prevent crashes
+ * @param options Socket creation options
+ * @returns The created socket
+ */
+export function createSocketWithErrorHandler(options: SafeSocketOptions): plugins.net.Socket {
+  const { port, host, onError, onConnect, timeout } = options;
+  
+  // Create socket with immediate error handler attachment
+  const socket = new plugins.net.Socket();
+  
+  // Attach error handler BEFORE connecting to catch immediate errors
+  socket.on('error', (error) => {
+    console.error(`Socket connection error to ${host}:${port}: ${error.message}`);
+    if (onError) {
+      onError(error);
+    }
+  });
+  
+  // Attach connect handler if provided
+  if (onConnect) {
+    socket.on('connect', onConnect);
+  }
+  
+  // Set timeout if provided
+  if (timeout) {
+    socket.setTimeout(timeout);
+  }
+  
+  // Now attempt to connect - any immediate errors will be caught
+  socket.connect(port, host);
+  
+  return socket;
 }