feat(ai): add chart renderer, floating ball hook, and provider updates

- Add ai-chart-renderer for rendering charts in AI responses

- Add use-floating-ball hook for draggable AI assistant widget

- Update ai-assistant-widget, ai-chat-panel, ai-markdown-renderer, ai-provider-selector

- Update use-ai-chat-stream hook and prompt-templates service

src/modules/ai/components/ai-chat-panel.tsx

@@ -34,6 +34,8 @@ type AiChatPanelProps = {
   maxMessages?: number
   /** 建议提示词列表（空状态展示） */
   suggestedPrompts?: string[]
+  /** 视觉变体：card（默认卡片）/ widget（悬浮球内嵌，无边框，撑满容器） */
+  variant?: "card" | "widget"
 }
 
 /**
@@ -57,37 +59,13 @@ export function AiChatPanel({
   title,
   maxMessages = 50,
   suggestedPrompts,
+  variant = "card",
 }: AiChatPanelProps): React.ReactNode {
   const t = useTranslations("ai")
   const { messages, streaming, error, send, stop, clear } = useAiChatStream()
   const [input, setInput] = useState("")
   const scrollRef = useRef<HTMLDivElement>(null)
-  const storageKey = "ai-chat-history"
-  const persistTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
-
-  // 持久化对话历史（防抖 500ms，避免流式过程中频繁写入）
-  useEffect(() => {
-    if (messages.length === 0) return
-    // 流式过程中不写入，流结束后再写
-    if (streaming) return
-
-    if (persistTimerRef.current) {
-      clearTimeout(persistTimerRef.current)
-    }
-    persistTimerRef.current = setTimeout(() => {
-      try {
-        localStorage.setItem(storageKey, JSON.stringify(messages.slice(-20)))
-      } catch {
-        // 忽略写入错误
-      }
-    }, 500)
-
-    return () => {
-      if (persistTimerRef.current) {
-        clearTimeout(persistTimerRef.current)
-      }
-    }
-  }, [messages, streaming])
+  const isWidget = variant === "widget"
 
   // 自动滚动到底部
   useEffect(() => {
@@ -101,17 +79,18 @@ export function AiChatPanel({
       const trimmed = (content ?? input).trim()
       if (!trimmed || streaming || messages.length >= maxMessages) return
 
-      const contextPrefix = contextMessage
-        ? `Context:\n${contextMessage}\n\nUser question: ${trimmed}`
-        : trimmed
+      // 上下文信息合并到 systemPrompt 发送给 AI，用户气泡只显示真实输入
+      const fullSystemPrompt = contextMessage
+        ? `${systemPrompt ?? ""}\n\n[Page Context]\n${contextMessage}`.trim()
+        : systemPrompt
 
       const requestMessages: AiChatMessage[] = [
         ...messages,
-        { role: "user", content: contextPrefix },
+        { role: "user", content: trimmed },
       ]
 
       setInput("")
-      await send(requestMessages, { systemPrompt })
+      await send(requestMessages, { systemPrompt: fullSystemPrompt })
     },
     [input, streaming, messages, maxMessages, systemPrompt, contextMessage, send]
   )
@@ -126,11 +105,6 @@ export function AiChatPanel({
   const handleClear = (): void => {
     if (window.confirm(t("chat.clearConfirm"))) {
       clear()
-      try {
-        localStorage.removeItem(storageKey)
-      } catch {
-        // 忽略
-      }
       toast.success(t("chat.clear"))
     }
   }
@@ -149,6 +123,145 @@ export function AiChatPanel({
     t("chat.suggestedPrompts.teacher.2"),
   ]
 
+  // widget 变体：无边框、撑满容器、消息区自适应高度
+  if (isWidget) {
+    return (
+      <div className="flex h-full flex-col">
+        {error ? (
+          <div
+            className="mx-3 mt-3 rounded-md border border-destructive/30 bg-destructive/5 p-3 text-sm text-destructive"
+            role="alert"
+          >
+            {error}
+          </div>
+        ) : null}
+
+        {messages.length > 0 ? (
+          <div
+            ref={scrollRef}
+            className="flex-1 overflow-y-auto px-4 py-4"
+            aria-live="polite"
+            aria-relevant="additions text"
+          >
+            <div className="space-y-4">
+              {messages.map((message, index) => (
+                <div
+                  key={index}
+                  className={cn(
+                    "flex gap-2.5",
+                    message.role === "user" ? "justify-end" : "justify-start"
+                  )}
+                >
+                  {message.role === "assistant" ? (
+                    <span className="flex h-7 w-7 shrink-0 items-center justify-center rounded-full bg-gradient-to-br from-primary to-primary/80 text-primary-foreground">
+                      <Bot className="h-4 w-4" />
+                    </span>
+                  ) : (
+                    <span className="flex h-7 w-7 shrink-0 items-center justify-center rounded-full bg-muted text-muted-foreground">
+                      <User className="h-4 w-4" />
+                    </span>
+                  )}
+                  <div
+                    className={cn(
+                      "rounded-2xl px-3.5 py-2 text-sm max-w-[80%]",
+                      message.role === "user"
+                        ? "bg-primary text-primary-foreground rounded-tr-sm"
+                        : "bg-muted rounded-tl-sm"
+                    )}
+                  >
+                    {message.role === "assistant" ? (
+                      <AiMarkdownRenderer content={message.content} />
+                    ) : (
+                      <p className="whitespace-pre-wrap">{message.content}</p>
+                    )}
+                  </div>
+                </div>
+              ))}
+              {streaming ? (
+                <div className="flex gap-2.5 justify-start">
+                  <span className="flex h-7 w-7 shrink-0 items-center justify-center rounded-full bg-gradient-to-br from-primary to-primary/80 text-primary-foreground">
+                    <Bot className="h-4 w-4" />
+                  </span>
+                  <div className="rounded-2xl rounded-tl-sm px-3.5 py-2 text-sm bg-muted">
+                    <span className="inline-flex gap-1">
+                      <span className="h-1.5 w-1.5 animate-bounce rounded-full bg-muted-foreground/60 [animation-delay:-0.3s]" />
+                      <span className="h-1.5 w-1.5 animate-bounce rounded-full bg-muted-foreground/60 [animation-delay:-0.15s]" />
+                      <span className="h-1.5 w-1.5 animate-bounce rounded-full bg-muted-foreground/60" />
+                    </span>
+                  </div>
+                </div>
+              ) : null}
+            </div>
+          </div>
+        ) : (
+          <div className="flex flex-1 flex-col items-center justify-center px-6 py-8">
+            <span className="flex h-14 w-14 items-center justify-center rounded-full bg-gradient-to-br from-primary to-primary/80 text-primary-foreground shadow-md mb-3">
+              <Sparkles className="h-7 w-7" />
+            </span>
+            <p className="text-base font-medium mb-1">{t("widget.welcome")}</p>
+            <p className="text-sm text-muted-foreground mb-4 text-center">{t("widget.welcomeDesc")}</p>
+            <div className="flex flex-wrap gap-2 justify-center max-w-sm">
+              {defaultSuggestedPrompts.map((prompt, index) => (
+                <Button
+                  key={index}
+                  type="button"
+                  variant="outline"
+                  size="sm"
+                  className="text-xs rounded-full"
+                  onClick={() => handleSuggestedPrompt(prompt)}
+                >
+                  {prompt}
+                </Button>
+              ))}
+            </div>
+          </div>
+        )}
+
+        <div className="border-t p-3">
+          <div className="flex items-end gap-2">
+            <Textarea
+              value={input}
+              onChange={(e) => setInput(e.target.value)}
+              onKeyDown={handleKeyDown}
+              placeholder={placeholder ?? t("chat.placeholder")}
+              className="min-h-10 max-h-32 resize-none rounded-2xl"
+              disabled={streaming || messages.length >= maxMessages}
+              aria-label={t("chat.inputLabel")}
+            />
+            {streaming ? (
+              <Button
+                type="button"
+                size="icon"
+                variant="destructive"
+                className="rounded-full shrink-0"
+                onClick={stop}
+                aria-label={t("chat.stopGeneration")}
+              >
+                <Square className="h-4 w-4" />
+              </Button>
+            ) : (
+              <Button
+                type="button"
+                size="icon"
+                className="rounded-full shrink-0"
+                onClick={() => void handleSend()}
+                disabled={!input.trim() || messages.length >= maxMessages}
+                aria-label={t("chat.send")}
+              >
+                <Send className="h-4 w-4" />
+              </Button>
+            )}
+          </div>
+          {messages.length >= maxMessages ? (
+            <p className="text-xs text-muted-foreground text-center mt-2">
+              {t("chat.maxReached")}
+            </p>
+          ) : null}
+        </div>
+      </div>
+    )
+  }
+
   return (
     <Card>
       <CardHeader>