feat: support minimax model (#185)

* feat: support minimax model with XML wrapping fix

- Add wrapWithMxFile utility to properly wrap XML for draw.io
- Fix 'Not a diagram file' error when model generates raw <root> XML
- Add supportsPromptCaching check for conditional caching
- Only enable Bedrock prompt caching for Claude models

* docs: update model mention to minimax-m2 across About pages and READMEs

- Update tooltip in chat-panel.tsx to mention minimax-m2 model change
- Update English, Chinese, and Japanese About pages with model change info
- Update English, Chinese, and Japanese READMEs with demo site model note

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Co-authored-by: dayuan.jiang <jiangdy@amazon.co.jp>

lib/ai-providers.ts

@@ -283,3 +283,17 @@ export function getAIModel(): ModelConfig {
 
     return { model, providerOptions, headers, modelId }
 }
+
+/**
+ * Check if a model supports prompt caching.
+ * Currently only Claude models on Bedrock support prompt caching.
+ */
+export function supportsPromptCaching(modelId: string): boolean {
+    // Bedrock prompt caching is supported for Claude models
+    return (
+        modelId.includes("claude") ||
+        modelId.includes("anthropic") ||
+        modelId.startsWith("us.anthropic") ||
+        modelId.startsWith("eu.anthropic")
+    )
+}