feat(extension): 侧边栏接入思维导图（markmap）与 RAG 问答（P3 + P4）

任务完成（status === SUCCESS）后，侧边栏顶部出现 Markdown / 思维导图 / AI 问答 三个 tab：

- 思维导图：用 markmap-lib + markmap-view 把 markdown 转成可缩放思维导图
- AI 问答：
  · 进入 tab 自动调 /api/chat/index 触发后台索引，按 2s 间隔轮询 /api/chat/status
  · 索引完成后开放输入框；调 /api/chat/ask 时带上 settings 里的默认 provider/model + 完整 history
  · Cmd/Ctrl + Enter 发送
  · 回答用 markdown-it 渲染，user 气泡用纯文本
- 切换任务时清空对话历史并重新检查索引

logic/api.ts 补 indexChatTask / getChatStatus / askChat 三件套。

依赖新增：markmap-lib, markmap-view（生产依赖）

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

BillNote_extension/src/components/ChatPanel.vue

@@ -0,0 +1,156 @@
+<script setup lang="ts">
+import { computed, nextTick, onMounted, onUnmounted, ref, watch } from 'vue'
+import MarkdownIt from 'markdown-it'
+import { askChat, getChatStatus, indexChatTask, type ChatMessage } from '~/logic/api'
+import { settings } from '~/logic/storage'
+
+const props = defineProps<{ taskId: string }>()
+
+const md = new MarkdownIt({ html: false, linkify: true, breaks: true })
+
+const messages = ref<ChatMessage[]>([])
+const draft = ref('')
+const sending = ref(false)
+const indexState = ref<'idle' | 'indexing' | 'indexed' | 'failed' | 'unknown'>('unknown')
+const error = ref('')
+const scrollEl = ref<HTMLElement | null>(null)
+let pollTimer: ReturnType<typeof setTimeout> | null = null
+
+const ready = computed(() => indexState.value === 'indexed')
+const canSend = computed(() => ready.value && draft.value.trim().length > 0 && !sending.value && !!settings.value.providerId && !!settings.value.modelName)
+
+async function pollIndex() {
+  try {
+    const res = await getChatStatus(props.taskId)
+    indexState.value = res.status
+    if (res.status === 'indexing')
+      pollTimer = setTimeout(pollIndex, 2000)
+  }
+  catch (e) {
+    error.value = (e as Error).message
+    indexState.value = 'failed'
+  }
+}
+
+async function ensureIndexed() {
+  error.value = ''
+  indexState.value = 'unknown'
+  try {
+    const status = await getChatStatus(props.taskId)
+    indexState.value = status.status
+    if (status.indexed)
+      return
+    indexState.value = 'indexing'
+    await indexChatTask(props.taskId)
+    pollIndex()
+  }
+  catch (e) {
+    error.value = (e as Error).message
+    indexState.value = 'failed'
+  }
+}
+
+async function send() {
+  if (!canSend.value)
+    return
+  const question = draft.value.trim()
+  draft.value = ''
+  messages.value.push({ role: 'user', content: question })
+  await scrollDown()
+  sending.value = true
+  try {
+    const res = await askChat({
+      task_id: props.taskId,
+      question,
+      history: messages.value.slice(0, -1),
+      provider_id: settings.value.providerId,
+      model_name: settings.value.modelName,
+    }) as { answer?: string, content?: string, message?: string } | string
+    const reply = typeof res === 'string'
+      ? res
+      : (res.answer ?? res.content ?? res.message ?? JSON.stringify(res))
+    messages.value.push({ role: 'assistant', content: reply })
+    await scrollDown()
+  }
+  catch (e) {
+    messages.value.push({ role: 'assistant', content: `❌ 调用失败：${(e as Error).message}` })
+  }
+  finally {
+    sending.value = false
+  }
+}
+
+async function scrollDown() {
+  await nextTick()
+  if (scrollEl.value)
+    scrollEl.value.scrollTop = scrollEl.value.scrollHeight
+}
+
+watch(() => props.taskId, () => {
+  messages.value = []
+  if (pollTimer) {
+    clearTimeout(pollTimer)
+    pollTimer = null
+  }
+  ensureIndexed()
+}, { immediate: false })
+
+onMounted(ensureIndexed)
+onUnmounted(() => {
+  if (pollTimer)
+    clearTimeout(pollTimer)
+})
+</script>
+
+<template>
+  <div class="flex flex-col h-full bg-white">
+    <header class="px-2 py-1 text-xs border-b flex items-center gap-2">
+      <span v-if="indexState === 'indexed'" class="tag bg-green-100 text-green-700">已索引</span>
+      <span v-else-if="indexState === 'indexing'" class="tag bg-yellow-100 text-yellow-700">索引中…</span>
+      <span v-else-if="indexState === 'failed'" class="tag bg-red-100 text-red-700">索引失败</span>
+      <span v-else class="tag bg-gray-100 text-gray-500">检查中…</span>
+      <button class="ml-auto text-xs text-gray-500 hover:text-gray-800" @click="ensureIndexed">
+        重新索引
+      </button>
+    </header>
+
+    <div v-if="error" class="text-xs text-red-600 px-2 py-1">{{ error }}</div>
+
+    <div ref="scrollEl" class="flex-1 overflow-auto px-2 py-2 flex flex-col gap-2">
+      <div v-if="messages.length === 0 && ready" class="text-xs text-gray-400 italic">
+        基于这条笔记的全文 + 视频元信息提问，例如：「这个视频的核心论点是什么？」
+      </div>
+      <div
+        v-for="(m, i) in messages"
+        :key="i"
+        class="text-sm"
+      >
+        <div
+          class="inline-block max-w-[90%] px-3 py-2 rounded"
+          :class="m.role === 'user'
+            ? 'bg-blue-600 text-white ml-auto block'
+            : 'bg-gray-100 text-gray-800'"
+        >
+          <div v-if="m.role === 'assistant'" v-html="md.render(m.content)" class="prose prose-sm max-w-none" />
+          <div v-else class="whitespace-pre-wrap break-words">{{ m.content }}</div>
+        </div>
+      </div>
+      <div v-if="sending" class="text-xs text-gray-500 italic">思考中…</div>
+    </div>
+
+    <footer class="border-t p-2 flex gap-2">
+      <textarea
+        v-model="draft"
+        class="input flex-1 resize-none"
+        rows="2"
+        :placeholder="ready ? '问点什么…（Cmd/Ctrl + Enter 发送）' : '索引完成后才能问答'"
+        :disabled="!ready"
+        @keydown.enter.exact.meta.prevent="send"
+        @keydown.enter.exact.ctrl.prevent="send"
+      />
+      <button class="btn-primary" :disabled="!canSend" @click="send">
+        {{ sending ? '…' : '发送' }}
+      </button>
+    </footer>
+  </div>
+</template>

BillNote_extension/src/components/MindMap.vue

@@ -0,0 +1,32 @@
+<script setup lang="ts">
+import { onMounted, ref, watch } from 'vue'
+import { Transformer } from 'markmap-lib'
+import { Markmap } from 'markmap-view'
+import { absolutizeMarkdownImages } from '~/logic/api'
+
+const props = defineProps<{ markdown: string }>()
+
+const svgRef = ref<SVGSVGElement | null>(null)
+let mm: Markmap | null = null
+const transformer = new Transformer()
+
+function render() {
+  if (!svgRef.value)
+    return
+  const md = absolutizeMarkdownImages(props.markdown || '')
+  const { root } = transformer.transform(md)
+  if (!mm)
+    mm = Markmap.create(svgRef.value, undefined, root)
+  else
+    mm.setData(root).then(() => mm?.fit())
+}
+
+onMounted(render)
+watch(() => props.markdown, render)
+</script>
+
+<template>
+  <div class="w-full h-full bg-white rounded border overflow-hidden">
+    <svg ref="svgRef" class="w-full h-full" />
+  </div>
+</template>