feat: 增强聊天 UI 与终端配置

- 重构消息列表、思考块与工具调用块样式
- ChatContext 支持 agent 分段与 markdown 渲染优化
- 后端增加 PI 命令配置与 Web 终端改进
- 新增 run-backend.sh 启动脚本，忽略 backend/dist 构建产物

backend/cmd/server/main.go

@@ -27,16 +27,16 @@ func main() {
 	defer database.Close()
 	log.Printf("[sproutclaw-web] db: %s", database.DbPath)
 
-	// pi CLI RPC client
+	// SproutClaw CLI RPC client
 	piClient, err := rpc.NewClient(cfg.PiCmd, cfg.PiArgs, cfg.RepoRoot, cfg.AgentDir, func(code int) {
 		if code != 0 {
-			log.Printf("[sproutclaw-web] pi CLI exited with code %d, shutting down", code)
+			log.Printf("[sproutclaw-web] SproutClaw CLI exited with code %d, shutting down", code)
 			os.Exit(1)
 		}
 		os.Exit(0)
 	})
 	if err != nil {
-		log.Fatalf("pi client: %v", err)
+		log.Fatalf("SproutClaw client: %v", err)
 	}
 	defer piClient.Stop()