fix(docs): update Anthropic model name and add version warnings (#32807)

**Description:** This PR fixes the broken Anthropic model example in the
documentation introduction page and adds a comment field to display
model version warnings in code blocks. The changes ensure that users can
successfully run the example code and are reminded to check for the
latest model versions.

**Issue:** https://github.com/langchain-ai/langchain/issues/32806

**Changes made:**
- Update Anthropic model from broken "claude-3-5-sonnet-latest" to
working "claude-3-7-sonnet-20250219"
- Add comment field to display model version warnings in code blocks
- Improve user experience by providing working examples and version
guidance

**Dependencies:** None required

docs/src/theme/ChatModelTabs.js

@@ -118,7 +118,8 @@ export default function ChatModelTabs(props) {
     {
       value: "anthropic",
       label: "Anthropic",
-      model: "claude-3-5-sonnet-latest",
+      model: "claude-3-7-sonnet-20250219",
+      comment: "# Note: Model versions may become outdated. Check https://docs.anthropic.com/en/docs/models-overview for latest versions",
       apiKeyName: "ANTHROPIC_API_KEY",
       packageName: "langchain[anthropic]",
     },
@@ -269,6 +270,9 @@ if not os.environ.get("${selectedTabItem.apiKeyName}"):
 
 ${llmVarName} = init_chat_model("${selectedTabItem.model}", model_provider="${selectedTabItem.value}"${selectedTabItem?.kwargs ? `, ${selectedTabItem.kwargs}` : ""})`;
 
+  // Add comment if available
+  const commentText = selectedTabItem?.comment ? selectedTabItem.comment + "\n\n" : "";
+
   return (
     <div>
       <CustomDropdown
@@ -282,7 +286,7 @@ ${llmVarName} = init_chat_model("${selectedTabItem.model}", model_provider="${se
         {`pip install -qU "${selectedTabItem.packageName}"`}
       </CodeBlock>
       <CodeBlock language="python">
-        {apiKeyText ? apiKeyText + "\n\n" + initModelText : initModelText}
+        {apiKeyText ? apiKeyText + "\n\n" + commentText + initModelText : commentText + initModelText}
       </CodeBlock>
     </div>
   );