fix: improve guard conditions and parameter validation

- Add stricter serverId validation in client message handling
- Enhance initialize method parameter validation to handle id=0 correctly
- Remove duplicate serverId guard condition

Author: ysfscream

src/client/mcp-client.ts

@@ -394,9 +394,7 @@ export class McpMqttClient extends EventEmitter {
     if (parts.length < 4) return
 
     const serverId = parts[2]
-    if (!serverId) return // Guard against undefined serverId
-
-    // const serverName = parts.slice(3).join('/') // Reconstruct hierarchical server name
+    if (!serverId) return
 
     if (!message.trim()) {
       // Empty message means server went offline

src/server/mcp-server.ts

@@ -317,7 +317,12 @@ export class McpMqttServer extends EventEmitter {
   private async handleControlMessage(message: string, clientId?: string): Promise<void> {
     const parsedMessage = JSON.parse(message)
 
-    if (parsedMessage.method === 'initialize' && parsedMessage.id && clientId) {
+    if (
+      parsedMessage.method === 'initialize' &&
+      parsedMessage.id !== undefined &&
+      parsedMessage.id !== null &&
+      clientId
+    ) {
       const request = parsedMessage as InitializeRequest
       const response = await this.handleInitialize(request, clientId)