docs: 添加使用示范和启动指南

- examples/demo_usage.py: Python 使用示范（openai SDK + requests）
- examples/demo_usage.go: Go 使用示范（net/http）
- run.md: 完整启动指南（前置条件、3种启动方式、API Key 配置、验证命令）

examples/demo_usage.py

@@ -0,0 +1,184 @@
+#!/usr/bin/env python3
+"""
+Edge AI Gateway 使用示范
+
+本文件演示其他应用如何通过 OpenAI 兼容 API 调用 Edge AI Gateway。
+支持两种方式：
+1. 使用 openai SDK（推荐）
+2. 使用 requests 库直接调用
+
+运行前请确保：
+- Edge AI Gateway 已启动 (默认 http://localhost:8080)
+- 已配置有效的 API Key
+"""
+
+# ============================================================
+# 方式一：使用 openai SDK（推荐）
+# ============================================================
+# pip install openai
+
+from openai import OpenAI
+
+client = OpenAI(
+    base_url="http://localhost:8080/v1",
+    api_key="test-key",  # 替换为你的 API Key
+)
+
+# --- 非流式对话 ---
+print("=== 非流式对话 ===")
+response = client.chat.completions.create(
+    model="general-chat",  # 逻辑模型名，网关自动路由到实际模型
+    messages=[
+        {"role": "system", "content": "你是一个简洁的助手"},
+        {"role": "user", "content": "你好，介绍一下你自己"},
+    ],
+    stream=False,
+)
+print(f"回复: {response.choices[0].message.content}")
+print(f"Token: 输入={response.usage.prompt_tokens}, 输出={response.usage.completion_tokens}")
+print()
+
+# --- 流式对话 (SSE) ---
+print("=== 流式对话 ===")
+stream = client.chat.completions.create(
+    model="fast-chat",
+    messages=[
+        {"role": "user", "content": "写一个 Python 的 hello world"},
+    ],
+    stream=True,
+)
+for chunk in stream:
+    delta = chunk.choices[0].delta.content
+    if delta:
+        print(delta, end="", flush=True)
+print("\n")
+
+# --- 带优先级的请求 (P0 最高) ---
+print("=== 高优先级请求 ===")
+response = client.chat.completions.create(
+    model="general-chat",
+    messages=[{"role": "user", "content": "1+1=?"}],
+    extra_headers={"X-Priority": "P0"},  # 通过 header 传递优先级
+)
+print(f"回复: {response.choices[0].message.content}")
+print()
+
+# --- 查看可用模型 ---
+print("=== 可用模型 ===")
+models = client.models.list()
+for m in models.data:
+    print(f"  - {m.id}")
+print()
+
+
+# ============================================================
+# 方式二：使用 requests 库直接调用
+# ============================================================
+# pip install requests
+
+import requests
+
+BASE_URL = "http://localhost:8080"
+API_KEY = "test-key"
+HEADERS = {
+    "Authorization": f"Bearer {API_KEY}",
+    "Content-Type": "application/json",
+}
+
+# --- 非流式 ---
+print("=== requests: 非流式 ===")
+resp = requests.post(
+    f"{BASE_URL}/v1/chat/completions",
+    headers=HEADERS,
+    json={
+        "model": "general-chat",
+        "messages": [{"role": "user", "content": "你好"}],
+        "stream": False,
+    },
+)
+data = resp.json()
+print(f"状态: {data.get('status')}")
+print(f"回复: {data['choices'][0]['message']['content']}")
+print(f"模型: {data.get('actual_model')}")
+print()
+
+# --- 流式 (SSE) ---
+print("=== requests: 流式 ===")
+resp = requests.post(
+    f"{BASE_URL}/v1/chat/completions",
+    headers=HEADERS,
+    json={
+        "model": "fast-chat",
+        "messages": [{"role": "user", "content": "讲个笑话"}],
+        "stream": True,
+    },
+    stream=True,
+)
+for line in resp.iter_lines():
+    if line:
+        line = line.decode("utf-8")
+        if line.startswith("data: ") and line != "data: [DONE]":
+            import json
+            chunk = json.loads(line[6:])
+            delta = chunk["choices"][0]["delta"].get("content", "")
+            if delta:
+                print(delta, end="", flush=True)
+print("\n")
+
+# --- 会话管理 ---
+print("=== 会话管理 ===")
+# 创建会话
+resp = requests.post(
+    f"{BASE_URL}/v1/sessions",
+    headers=HEADERS,
+    json={"application_id": "my-app", "user_id": "user123"},
+)
+session = resp.json()
+session_id = session["session_id"]
+print(f"创建会话: {session_id}")
+
+# 查询会话
+resp = requests.get(
+    f"{BASE_URL}/v1/sessions/{session_id}",
+    headers=HEADERS,
+)
+print(f"会话信息: {resp.json()}")
+
+# 删除会话
+resp = requests.delete(
+    f"{BASE_URL}/v1/sessions/{session_id}",
+    headers=HEADERS,
+)
+print(f"删除会话: HTTP {resp.status_code}")
+print()
+
+# --- 错误处理 ---
+print("=== 错误处理 ===")
+# 无认证
+resp = requests.get(f"{BASE_URL}/v1/models")
+print(f"无认证: {resp.status_code} - {resp.json()['error']['code']}")
+
+# 无效 key
+resp = requests.get(
+    f"{BASE_URL}/v1/models",
+    headers={"Authorization": "Bearer invalid-key"},
+)
+print(f"无效key: {resp.status_code} - {resp.json()['error']['code']}")
+
+# 缺少 model
+resp = requests.post(
+    f"{BASE_URL}/v1/chat/completions",
+    headers=HEADERS,
+    json={"messages": [{"role": "user", "content": "hi"}]},
+)
+print(f"缺少model: {resp.status_code} - {resp.json()['error']['code']}")
+
+# 未知 model
+resp = requests.post(
+    f"{BASE_URL}/v1/chat/completions",
+    headers=HEADERS,
+    json={"model": "nonexistent", "messages": [{"role": "user", "content": "hi"}]},
+)
+print(f"未知model: {resp.status_code} - {resp.json()['error']['code']}")
+
+print("\n✅ 示范完成！")