feat: 新增 core/agents 模块和 nanobot

- 新增 agents 模块，包含 agent、api、skills 等子模块
- 新增 nanobot 项目，支持多渠道集成
- 添加启动脚本 start-all.bat 和 start-all.sh

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/agents/.env.example

@@ -0,0 +1,27 @@
+# X-Agents Python Agent Environment Configuration
+
+# API Settings
+API_HOST=0.0.0.0
+API_PORT=8001
+
+# Go Backend URL (for tool sync)
+GO_BACKEND_URL=http://localhost:8080
+
+# LLM Provider (openai/anthropic)
+LLM_PROVIDER=openai
+
+# LLM API Key (required for actual LLM calls)
+LLM_API_KEY=your-api-key-here
+
+# LLM Model
+LLM_MODEL=gpt-4o
+
+# Optional: Custom LLM Base URL (for proxy/alternative endpoints)
+# LLM_BASE_URL=https://api.openai.com/v1
+
+# Workspace for agent files
+WORKSPACE=./workspace
+
+# Agent settings
+MAX_ITERATIONS=10
+TEMPERATURE=0.7