Add documentation for the new Agent feature and update sidebar positions for Metrics and API categories. Adjust code examples in various API documentation to reflect correct paths and improve clarity. Enhance the Agent class with an equals and hash code method for better functionality.

src/main/java/io/github/ollama4j/agent/Agent.java

@@ -265,6 +265,7 @@ public class Agent {
     @Data
     @Setter
     @Getter
+    @EqualsAndHashCode(callSuper = false)
     private static class AgentToolSpec extends Tools.ToolSpec {
         /** Fully qualified class name of the tool's {@link ToolFunction} implementation */
         private String toolFunctionFQCN = null;