Browse the knowledge base from a single side panel menu

Add a read-only view of backend/knowledge_base/**.md so the files that get
injected into the system prompt can be inspected from the GUI:

- GET /api/kb/files lists the Markdown files (title, preview, size, mtime and
  whether the file is already embedded), GET /api/kb/file returns one in full.
  Paths are resolved against the knowledge base directory and rejected unless
  they stay inside it and end in .md.
- KnowledgeBasePanel.vue groups the files by folder (collapsible, so web_search
  can be folded away), filters by title/path/preview and renders the selected
  file with MarkdownContent.

The header had grown to four side panel toggles, so collapse them into one
menu: panels.ts now holds the list of panels along with the component each one
renders, App.vue picks it with <component :is>, and SidePanelMenu.vue shows the
active panel on its button. Re-picking the open panel (or "パネルを閉じる")
closes it; a click outside or Esc closes just the menu.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/components/KnowledgeBasePanel.vue

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+<script setup lang="ts">
+import { onMounted } from 'vue'
+import MarkdownContent from './MarkdownContent.vue'
+import { useKnowledgeBaseStore } from '../stores/knowledgeBase'
+
+const store = useKnowledgeBaseStore()
+
+onMounted(() => store.load())
+
+function formatSize(bytes: number): string {
+  return bytes < 1024 ? `${bytes} B` : `${Math.round(bytes / 1024)} KB`
+}
+
+function formatDate(iso: string): string {
+  return new Date(iso).toLocaleString('ja-JP', {
+    year: 'numeric', month: '2-digit', day: '2-digit', hour: '2-digit', minute: '2-digit',
+  })
+}
+</script>
+
+<template>
+  <div class="kb-panel">
+    <div class="toolbar">
+      <button v-if="store.openFile" class="back-btn" title="一覧に戻る" @click="store.close()">←</button>
+      <span class="title">{{ store.openFile ? store.openFile.title : 'ナレッジベース' }}</span>
+      <button class="reload-btn" :disabled="store.loading" title="再読み込み" @click="store.load()">⟳</button>
+    </div>
+
+    <div v-if="store.error" class="error">⚠ {{ store.error }}</div>
+
+    <!-- ファイル表示 -->
+    <template v-if="store.openFile">
+      <div class="file-meta">
+        <code class="path">{{ store.openFile.path }}</code>
+        <span>{{ formatSize(store.openFile.size) }} / {{ formatDate(store.openFile.updated_at) }}</span>
+      </div>
+      <div class="content">
+        <MarkdownContent :content="store.openFile.content" />
+      </div>
+    </template>
+
+    <!-- 一覧 -->
+    <template v-else>
+      <div class="search">
+        <input v-model="store.filter" type="search" placeholder="タイトル・パス・本文の先頭で絞り込み">
+        <span class="count">{{ store.filteredFiles.length }} / {{ store.files.length }}</span>
+      </div>
+
+      <div v-if="store.files.length === 0 && !store.loading" class="empty">
+        ナレッジベースに .md ファイルがありません。<br>
+        <code>backend/knowledge_base/</code> に置くと自動で読み込まれます。
+      </div>
+
+      <div v-else class="list">
+        <div v-for="group in store.groups" :key="group.directory" class="group">
+          <button class="group-header" @click="store.toggleGroup(group.directory)">
+            <span class="arrow">{{ store.collapsed.has(group.directory) ? '▸' : '▾' }}</span>
+            <span class="dir">{{ group.directory || '(ルート)' }}</span>
+            <span class="group-count">{{ group.files.length }}</span>
+          </button>
+          <template v-if="!store.collapsed.has(group.directory)">
+            <button
+              v-for="file in group.files"
+              :key="file.path"
+              class="file"
+              @click="store.open(file.path)"
+            >
+              <div class="file-title">
+                <span class="dot" :class="{ indexed: file.indexed }"
+                  :title="file.indexed ? '埋め込み済み（話題に応じて自動で参照される）' : '未埋め込み（次回のチャット時に取り込まれる）'" />
+                <span class="name">{{ file.title }}</span>
+                <span class="size">{{ formatSize(file.size) }}</span>
+              </div>
+              <div v-if="file.preview" class="file-preview">{{ file.preview }}</div>
+            </button>
+          </template>
+        </div>
+      </div>
+
+      <div class="hint">
+        <code>backend/knowledge_base/</code> 配下の Markdown です。話題との類似度が高い上位数件が、
+        システムプロンプトに<strong>全文</strong>そのまま注入されます。
+        <code>web_search/</code> は AI の Web 検索結果が自動保存されたものです。
+      </div>
+    </template>
+  </div>
+</template>
+
+<style scoped>
+.kb-panel {
+  display: flex;
+  flex-direction: column;
+  height: 100%;
+  overflow: hidden;
+  background: #111;
+}
+.toolbar {
+  display: flex; align-items: center; gap: 8px;
+  padding: 10px 12px; border-bottom: 1px solid #2a2a2a; flex-shrink: 0;
+}
+.title {
+  font-size: 13px; font-weight: 600; color: #aaa; flex: 1;
+  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
+}
+.back-btn, .reload-btn {
+  background: none; border: 1px solid #444; color: #aaa;
+  border-radius: 5px; padding: 2px 8px; cursor: pointer; font-size: 13px;
+}
+.back-btn:hover, .reload-btn:hover:not(:disabled) { color: #fff; }
+.error { padding: 8px 12px; color: #f87171; font-size: 12px; }
+
+.search {
+  display: flex; align-items: center; gap: 8px;
+  padding: 8px 12px; border-bottom: 1px solid #1e1e1e; flex-shrink: 0;
+}
+.search input {
+  flex: 1; background: #1a1a1a; color: #ddd; border: 1px solid #333;
+  border-radius: 5px; padding: 4px 8px; font-size: 12px;
+}
+.search input:focus { outline: none; border-color: #2563eb; }
+.count { font-size: 11px; color: #555; white-space: nowrap; }
+
+.list { flex: 1; overflow-y: auto; padding-bottom: 4px; }
+.group-header {
+  display: flex; align-items: center; gap: 6px; width: 100%;
+  background: #171717; border: none; border-bottom: 1px solid #1e1e1e;
+  color: #888; font-size: 11px; padding: 5px 12px; cursor: pointer;
+  position: sticky; top: 0;
+}
+.group-header:hover { color: #ccc; }
+.arrow { font-size: 9px; }
+.dir { flex: 1; text-align: left; font-family: 'Consolas', monospace; }
+.group-count { color: #555; }
+
+.file {
+  display: block; width: 100%; text-align: left;
+  background: none; border: none; border-bottom: 1px solid #1a1a1a;
+  padding: 8px 12px; cursor: pointer;
+}
+.file:hover { background: #1a1a1a; }
+.file-title { display: flex; align-items: center; gap: 7px; }
+.dot {
+  width: 6px; height: 6px; border-radius: 50%; background: #444; flex-shrink: 0;
+}
+.dot.indexed { background: #22c55e; }
+.name {
+  flex: 1; color: #ddd; font-size: 12px;
+  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
+}
+.size { color: #555; font-size: 11px; white-space: nowrap; }
+.file-preview {
+  margin-top: 3px; padding-left: 13px; color: #666; font-size: 11px;
+  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
+}
+
+.file-meta {
+  display: flex; align-items: center; gap: 10px; justify-content: space-between;
+  padding: 6px 12px; border-bottom: 1px solid #1e1e1e;
+  color: #666; font-size: 11px; flex-shrink: 0;
+}
+.path {
+  color: #7dd3fc; font-family: 'Consolas', monospace;
+  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
+}
+.content { flex: 1; overflow-y: auto; padding: 12px 14px; color: #ddd; font-size: 13px; }
+
+.empty { padding: 20px; text-align: center; color: #555; font-size: 12px; line-height: 1.8; }
+.hint {
+  padding: 8px 12px; border-top: 1px solid #1e1e1e;
+  color: #666; font-size: 11px; line-height: 1.6; flex-shrink: 0;
+}
+.hint code { color: #9ca3af; font-family: 'Consolas', monospace; }
+</style>

frontend/src/components/SidePanelMenu.vue

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+<script setup lang="ts">
+import { computed, onMounted, onUnmounted, ref } from 'vue'
+import { SIDE_PANELS, type PanelId } from '../panels'
+
+const props = defineProps<{ active: PanelId | null }>()
+const emit = defineEmits<{ (e: 'select', panel: PanelId | null): void }>()
+
+const open = ref(false)
+const root = ref<HTMLElement | null>(null)
+
+const activePanel = computed(() => SIDE_PANELS.find((p) => p.id === props.active) ?? null)
+
+/** 項目を選ぶ。開いているパネルをもう一度選んだら閉じる（従来のトグルと同じ操作感）。 */
+function select(id: PanelId) {
+  emit('select', props.active === id ? null : id)
+  open.value = false
+}
+
+function close() {
+  emit('select', null)
+  open.value = false
+}
+
+function onDocumentPointerDown(e: PointerEvent) {
+  if (open.value && !root.value?.contains(e.target as Node)) open.value = false
+}
+
+function onKeydown(e: KeyboardEvent) {
+  if (e.key === 'Escape') open.value = false
+}
+
+onMounted(() => {
+  document.addEventListener('pointerdown', onDocumentPointerDown)
+  document.addEventListener('keydown', onKeydown)
+})
+onUnmounted(() => {
+  document.removeEventListener('pointerdown', onDocumentPointerDown)
+  document.removeEventListener('keydown', onKeydown)
+})
+</script>
+
+<template>
+  <div ref="root" class="panel-menu">
+    <button
+      class="menu-btn"
+      :class="{ active: activePanel !== null, open }"
+      :title="activePanel ? `${activePanel.label}を表示中` : 'パネルを開く'"
+      @click="open = !open"
+    >
+      <span class="menu-icon">{{ activePanel ? activePanel.icon : '☰' }}</span>
+      <span class="menu-label">{{ activePanel ? activePanel.label : 'パネル' }}</span>
+      <span class="caret">▾</span>
+    </button>
+
+    <div v-if="open" class="dropdown">
+      <button
+        v-for="panel in SIDE_PANELS"
+        :key="panel.id"
+        class="item"
+        :class="{ current: panel.id === active }"
+        @click="select(panel.id)"
+      >
+        <span class="item-icon">{{ panel.icon }}</span>
+        <span class="item-text">
+          <span class="item-label">{{ panel.label }}</span>
+          <span class="item-desc">{{ panel.description }}</span>
+        </span>
+        <span class="check">{{ panel.id === active ? '✓' : '' }}</span>
+      </button>
+      <button v-if="activePanel" class="item close-item" @click="close">
+        <span class="item-icon">✕</span>
+        <span class="item-text"><span class="item-label">パネルを閉じる</span></span>
+        <span class="check" />
+      </button>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.panel-menu { position: relative; }
+.menu-btn {
+  display: flex; align-items: center; gap: 6px;
+  background: #2a2a2a; color: #aaa; border: 1px solid #444;
+  border-radius: 6px; padding: 4px 12px; font-size: 13px; cursor: pointer;
+}
+.menu-btn:hover { color: #ddd; }
+.menu-btn.active { background: #1d3557; color: #93c5fd; border-color: #2563eb; }
+.menu-btn.open { border-color: #666; }
+.menu-btn.active.open { border-color: #3b82f6; }
+.menu-icon { font-size: 13px; line-height: 1; }
+.menu-label { white-space: nowrap; }
+.caret { font-size: 9px; color: #777; }
+
+.dropdown {
+  position: absolute; top: calc(100% + 6px); right: 0; z-index: 50;
+  min-width: 260px;
+  background: #1c1c1c; border: 1px solid #3a3a3a; border-radius: 8px;
+  padding: 4px; box-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
+}
+.item {
+  display: flex; align-items: center; gap: 10px; width: 100%;
+  background: none; border: none; border-radius: 6px;
+  padding: 7px 9px; cursor: pointer; text-align: left;
+}
+.item:hover { background: #262626; }
+.item.current { background: #1d3557; }
+.item-icon { font-size: 14px; width: 18px; text-align: center; flex-shrink: 0; }
+.item-text { flex: 1; display: flex; flex-direction: column; gap: 1px; overflow: hidden; }
+.item-label { color: #ddd; font-size: 13px; }
+.item.current .item-label { color: #93c5fd; }
+.item-desc {
+  color: #6b7280; font-size: 11px;
+  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
+}
+.check { color: #93c5fd; font-size: 11px; width: 10px; flex-shrink: 0; }
+.close-item { border-top: 1px solid #2a2a2a; border-radius: 0 0 6px 6px; margin-top: 2px; }
+.close-item .item-label { color: #888; }
+</style>