docs(readme): recommend pip install over prebuilt binary

Reorder the installation methods so "From PyPI" (pip install) is listed
first and marked as recommended, with the prebuilt binary moved to second
place. Mirror the change in README_zh.md to keep bilingual parity.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Sodawyx <sodawyx@126.com>

Author: Sodawyx

README.md

@@ -23,7 +23,13 @@ agents that you configure declaratively without writing or deploying any runtime
 
 ## Installation
 
-### Prebuilt binary (recommended)
+### From PyPI (recommended)
+
+```bash
+pip install agentrun-cli
+```
+
+### Prebuilt binary
 
 Download a single self-contained binary from [Releases](https://github.com/Serverless-Devs/agentrun-cli/releases). No Python required.
 
@@ -50,12 +56,6 @@ agentrun-<version>-<os>-<arch>.<ext>
 #      agentrun-0.1.0-windows-amd64.zip
 ```
 
-### From PyPI
-
-```bash
-pip install agentrun-cli
-```
-
 ### From source
 
 ```bash

README_zh.md

@@ -22,7 +22,13 @@ Agent）**：一种由平台托管、用户只需声明配置、无需编写或
 
 ## 安装
 
-### 预编译二进制（推荐）
+### 从 PyPI 安装（推荐）
+
+```bash
+pip install agentrun-cli
+```
+
+### 预编译二进制
 
 从 [Releases](https://github.com/Serverless-Devs/agentrun-cli/releases) 下载单文件二进制，无需 Python。
 
@@ -49,12 +55,6 @@ agentrun-<version>-<os>-<arch>.<ext>
 #      agentrun-0.1.0-windows-amd64.zip
 ```
 
-### 从 PyPI 安装
-
-```bash
-pip install agentrun-cli
-```
-
 ### 从源码安装
 
 ```bash