Add README for provider setup instructions

Added setup instructions for Codex and Claude Code integration with API.

README.md

@@ -0,0 +1,133 @@
+# Provider Setup
+
+用于一键配置 Codex 和 Claude Code 接入 `https://api.xi-xu.me`。
+
+## 功能
+
+### Codex
+
+会自动完成以下操作：
+
+- 写入 `~/.codex/config.toml`
+- 设置 provider 为 `xixu`
+- 配置 `XIXU_API_KEY` 环境变量
+
+### Claude Code
+
+会自动完成以下操作：
+
+- 写入 `~/.claude/settings.json`
+- 配置 `ANTHROPIC_AUTH_TOKEN`
+- 配置 `ANTHROPIC_BASE_URL`
+- 配置默认模型为 `gpt-5.4`
+
+---
+
+## Codex
+
+### Linux/macOS
+
+```bash
+bash <(curl -fsSL https://github.com/xixu-me/provider-setup/raw/refs/heads/main/codex.sh)
+````
+
+### Windows PowerShell
+
+```powershell
+powershell -ExecutionPolicy Bypass -Command "& ([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://github.com/xixu-me/provider-setup/raw/refs/heads/main/codex.ps1').Content))"
+```
+
+---
+
+## Claude Code
+
+### Linux/macOS
+
+```bash
+bash <(curl -fsSL https://github.com/xixu-me/provider-setup/raw/refs/heads/main/claude.sh)
+```
+
+### Windows PowerShell
+
+```powershell
+powershell -ExecutionPolicy Bypass -Command "& ([scriptblock]::Create((Invoke-WebRequest -UseBasicParsing 'https://github.com/xixu-me/provider-setup/raw/refs/heads/main/claude.ps1').Content))"
+```
+
+---
+
+## 配置内容
+
+### Codex
+
+写入：
+
+```toml
+model_provider = "xixu"
+
+[model_providers.xixu]
+name = "Xi Xu's AI Inference"
+base_url = "https://api.xi-xu.me/v1"
+env_key = "XIXU_API_KEY"
+```
+
+### Claude Code
+
+写入到 `~/.claude/settings.json` 的 `env`：
+
+```json
+{
+  "env": {
+    "ANTHROPIC_AUTH_TOKEN": "YOUR_API_KEY",
+    "ANTHROPIC_BASE_URL": "https://api.xi-xu.me",
+    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "gpt-5.4",
+    "ANTHROPIC_DEFAULT_OPUS_MODEL": "gpt-5.4",
+    "ANTHROPIC_DEFAULT_SONNET_MODEL": "gpt-5.4",
+    "CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC": "1",
+    "CLAUDE_CODE_SUBAGENT_MODEL": "gpt-5.4"
+  }
+}
+```
+
+---
+
+## 说明
+
+* 脚本默认会提示输入 API Key
+* 若对应配置文件已存在，会在保留其他配置的基础上更新目标字段
+* Windows 下用户级环境变量会持久化保存
+* Linux/macOS 下会写入当前 shell 配置文件以便后续生效
+
+---
+
+## 验证
+
+### Codex
+
+#### Linux/macOS
+
+```bash
+cat ~/.codex/config.toml
+echo $XIXU_API_KEY
+```
+
+#### Windows PowerShell
+
+```powershell
+Get-Content ~/.codex/config.toml
+$env:XIXU_API_KEY
+[System.Environment]::GetEnvironmentVariable("XIXU_API_KEY","User")
+```
+
+### Claude Code
+
+#### Linux/macOS
+
+```bash
+cat ~/.claude/settings.json
+```
+
+#### Windows PowerShell
+
+```powershell
+Get-Content ~/.claude/settings.json
+```