docs(#1735): add MvnRepository badge to README badge row

Slotted next to the Maven Central badge — both describe artifact
availability, keeping them adjacent makes the row's intent obvious.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Skobeltsyn

README.md

@@ -10,6 +10,7 @@
 <p align="center">
   <a href="https://github.com/Deep-CodeAI/Agents.KT/actions/workflows/ci.yml"><img src="https://github.com/Deep-CodeAI/Agents.KT/actions/workflows/ci.yml/badge.svg" alt="CI" /></a>
   <a href="https://central.sonatype.com/artifact/ai.deep-code/agents-kt"><img src="https://img.shields.io/maven-central/v/ai.deep-code/agents-kt?color=blue" alt="Maven Central" /></a>
+  <a href="https://mvnrepository.com/artifact/ai.deep-code/agents-kt"><img src="https://badges.mvnrepository.com/badge/ai.deep-code/agents-kt/badge.svg?label=MvnRepository" alt="MvnRepository" /></a>
   <a href="https://kotlinlang.org"><img src="https://img.shields.io/badge/Kotlin-2.1-7F52FF?logo=kotlin&logoColor=white" alt="Kotlin" /></a>
   <a href="https://openjdk.org"><img src="https://img.shields.io/badge/JDK-21+-orange" alt="JDK" /></a>
   <a href="LICENSE"><img src="https://img.shields.io/badge/License-MIT-blue.svg" alt="License: MIT" /></a>