initial commit: slides + practica_resueltos + README

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

slides/pages/agents/13.md

@@ -0,0 +1,36 @@
+---
+layout: default
+---
+
+# Middleware Custom
+
+<div class="mt-4 text-xs">
+
+<v-click>
+
+```typescript
+import { createAgent, createMiddleware } from "langchain";
+
+const loggingMiddleware = createMiddleware({
+  name: "LoggingMiddleware",
+  beforeModel: (state) => {
+    console.log(`Llamando modelo con ${state.messages.length} mensajes`);
+    return;  // No modificar estado
+  },
+  afterModel: (state) => {
+    const lastMsg = state.messages[state.messages.length - 1];
+    console.log(`Modelo respondió: ${lastMsg.content?.slice(0, 50)}...`);
+    return;
+  },
+});
+
+const agent = createAgent({
+  model: "mistral:mistral-large-latest",
+  tools: [weatherTool],
+  middleware: [loggingMiddleware],
+});
+```
+
+</v-click>
+
+</div>