api: implement anthropic api (#13600)

* api: add Anthropic Messages API compatibility layer

Add middleware to support the Anthropic Messages API format at /v1/messages.
This enables tools like Claude Code to work with Ollama local and cloud models through the
Anthropic API interface.

server/routes.go

@@ -1544,6 +1544,9 @@ func (s *Server) GenerateRoutes(rc *ollama.Registry) (http.Handler, error) {
 	r.GET("/v1/models/:model", middleware.RetrieveMiddleware(), s.ShowHandler)
 	r.POST("/v1/responses", middleware.ResponsesMiddleware(), s.ChatHandler)
 
+	// Inference (Anthropic compatibility)
+	r.POST("/v1/messages", middleware.AnthropicMessagesMiddleware(), s.ChatHandler)
+
 	if rc != nil {
 		// wrap old with new
 		rs := &registry.Local{