add vitepress docs

docs/demos/ai/mock-sse.ts

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+/**
+ * 演示专用的假 SSE 流。
+ *
+ * `useAiChat` 要求 `request` 返回一个 `Response`，真实的实现由后端提供。
+ * 这里用 ReadableStream 按内置协议逐条吐出事件，让文档站无需后端也能跑通
+ * 流式对话的完整链路。
+ *
+ * 内置协议的事件名与载荷字段（见 `parseDefaultEvent` / `extractText` 等）：
+ * - `thinking`    载荷取 `thought` / `thinking` / `reasoning`
+ * - `answer`      载荷取 `answer` / `text` / `content`
+ * - `tool-status` 载荷取 `text` / `message` / `status`
+ * - `citation`    载荷为引用对象
+ * - `done`        载荷可带 `conversationId` 与 `duration`
+ */
+
+/** 单条 SSE 事件。 */
+interface MockEvent {
+	event: string;
+	data: Record<string, unknown>;
+}
+
+/** 每个事件之间的间隔，模拟真实的流式节奏。 */
+const STEP_DELAY = 420;
+
+function buildEvents(question: string): MockEvent[] {
+	return [
+		{ event: "thinking", data: { thought: `先理解问题：「${question}」` } },
+		{ event: "thinking", data: { thought: "然后确认需要的数据口径与时间范围。" } },
+		{ event: "tool-status", data: { text: "正在查询数据" } },
+		{ event: "answer", data: { text: "根据当前口径，" } },
+		{ event: "answer", data: { text: `关于「${question}」的结论如下：` } },
+		{ event: "answer", data: { text: "\n\n- 近 30 天整体**环比上升 12%**" } },
+		{ event: "answer", data: { text: "\n- 其中移动端贡献了主要增量" } },
+		{ event: "citation", data: { source: "分析中心", dataDomain: "订单域", timeRange: "近 30 天" } },
+		{ event: "done", data: { conversationId: "demo-conversation", duration: STEP_DELAY * 9 } }
+	];
+}
+
+function sleep(ms: number): Promise<void> {
+	return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+/**
+ * 生成一段假的流式回复。
+ *
+ * @param question 用户提问，会回显在回答里
+ * @param signal   取消信号，用户点「停止」时中断
+ */
+export function createMockReply(question: string, signal?: AbortSignal): Response {
+	const encoder = new TextEncoder();
+	const events = buildEvents(question);
+	let index = 0;
+
+	const stream = new ReadableStream<Uint8Array>({
+		async pull(controller) {
+			if (signal?.aborted) {
+				controller.error(new DOMException("已停止生成", "AbortError"));
+				return;
+			}
+			if (index >= events.length) {
+				controller.close();
+				return;
+			}
+			const item = events[index];
+			index += 1;
+			controller.enqueue(encoder.encode(`event: ${item.event}\ndata: ${JSON.stringify(item.data)}\n\n`));
+			await sleep(STEP_DELAY);
+		}
+	});
+
+	return new Response(stream, {
+		headers: { "Content-Type": "text/event-stream" }
+	});
+}
+
+/** 构造一条用于静态展示的消息。 */
+export function createMessage(
+	id: number,
+	role: "user" | "assistant",
+	content: string,
+	extra: Partial<{ thinkingList: Array<{ id: number; content: string }>; citationList: unknown[] }> = {}
+) {
+	return {
+		id,
+		role,
+		content,
+		thinkingList: extra.thinkingList ?? [],
+		citationList: extra.citationList ?? [],
+		createdAt: Date.now() - (10 - id) * 60_000,
+		statusText: "",
+		duration: role === "assistant" ? 2400 : undefined
+	};
+}