Add global knowledge base with RAG search

- KB module: fastembed (AllMiniLML6V2) for CPU embedding, SQLite for
  vector storage with brute-force cosine similarity search
- Chunking by ## headings, embeddings stored as BLOB in kb_chunks table
- API: GET/PUT /api/kb for full-text read/write with auto re-indexing
- Agent tools: kb_search (top-5 semantic search) and kb_read (full text)
  available in both planning and execution phases
- Frontend: Settings menu in sidebar footer, KB editor as independent
  view with markdown textarea and save button
- Also: extract shared db_err/ApiResult to api/mod.rs, add context
  management design doc

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/api.ts

@@ -75,4 +75,12 @@ export const api = {
 
   deleteTimer: (timerId: string) =>
     request<void>(`/timers/${timerId}`, { method: 'DELETE' }),
+
+  getKb: () => request<{ content: string }>('/kb'),
+
+  putKb: (content: string) =>
+    request<{ content: string }>('/kb', {
+      method: 'PUT',
+      body: JSON.stringify({ content }),
+    }),
 }

web/src/components/AppLayout.vue

@@ -4,6 +4,7 @@ import Sidebar from './Sidebar.vue'
 import WorkflowView from './WorkflowView.vue'
 import ReportView from './ReportView.vue'
 import CreateForm from './CreateForm.vue'
+import KbEditor from './KbEditor.vue'
 import { api } from '../api'
 import type { Project } from '../types'
 
@@ -12,6 +13,7 @@ const selectedProjectId = ref('')
 const reportWorkflowId = ref('')
 const error = ref('')
 const creating = ref(false)
+const showKb = ref(false)
 
 const isReportPage = computed(() => !!reportWorkflowId.value)
 
@@ -54,6 +56,7 @@ function onSelectProject(id: string) {
   selectedProjectId.value = id
   reportWorkflowId.value = ''
   creating.value = false
+  showKb.value = false
   history.pushState(null, '', `/projects/${id}`)
 }
 
@@ -110,10 +113,12 @@ async function onDeleteProject(id: string) {
       @select="onSelectProject"
       @create="onStartCreate"
       @delete="onDeleteProject"
+      @openKb="showKb = true; selectedProjectId = ''; creating = false"
     />
     <main class="main-content">
       <div v-if="error" class="error-banner" @click="error = ''">{{ error }}</div>
-      <div v-if="creating" class="empty-state">
+      <KbEditor v-if="showKb" />
+      <div v-else-if="creating" class="empty-state">
         <CreateForm @submit="onConfirmCreate" @cancel="creating = false" />
       </div>
       <div v-else-if="!selectedProjectId" class="empty-state">

web/src/components/KbEditor.vue

@@ -0,0 +1,130 @@
+<script setup lang="ts">
+import { ref, onMounted } from 'vue'
+import { api } from '../api'
+
+const content = ref('')
+const saving = ref(false)
+const loading = ref(true)
+const message = ref('')
+
+onMounted(async () => {
+  try {
+    const kb = await api.getKb()
+    content.value = kb.content
+  } catch (e: any) {
+    message.value = 'Failed to load: ' + e.message
+  } finally {
+    loading.value = false
+  }
+})
+
+async function save() {
+  saving.value = true
+  message.value = ''
+  try {
+    await api.putKb(content.value)
+    message.value = 'Saved & indexed'
+    setTimeout(() => { message.value = '' }, 2000)
+  } catch (e: any) {
+    message.value = 'Error: ' + e.message
+  } finally {
+    saving.value = false
+  }
+}
+</script>
+
+<template>
+  <div class="kb-view">
+    <div class="kb-header">
+      <h2>Knowledge Base</h2>
+      <div class="kb-actions">
+        <span v-if="message" class="kb-message">{{ message }}</span>
+        <button class="btn-save" @click="save" :disabled="saving">
+          {{ saving ? 'Saving...' : 'Save' }}
+        </button>
+      </div>
+    </div>
+    <div v-if="loading" class="kb-loading">Loading...</div>
+    <textarea
+      v-else
+      v-model="content"
+      class="kb-textarea"
+      placeholder="Write your knowledge base in Markdown...&#10;&#10;Use ## headings to split into searchable chunks."
+      spellcheck="false"
+    />
+  </div>
+</template>
+
+<style scoped>
+.kb-view {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.kb-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 16px 20px;
+  border-bottom: 1px solid var(--border);
+}
+
+.kb-header h2 {
+  font-size: 16px;
+  font-weight: 600;
+  margin: 0;
+}
+
+.kb-actions {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+}
+
+.kb-message {
+  font-size: 12px;
+  color: var(--accent);
+}
+
+.btn-save {
+  padding: 6px 16px;
+  background: var(--accent);
+  color: var(--bg-primary);
+  border: none;
+  border-radius: 6px;
+  font-size: 13px;
+  cursor: pointer;
+}
+
+.btn-save:disabled {
+  opacity: 0.5;
+}
+
+.kb-loading {
+  flex: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  color: var(--text-secondary);
+}
+
+.kb-textarea {
+  flex: 1;
+  padding: 20px;
+  background: var(--bg-primary);
+  color: var(--text-primary);
+  border: none;
+  resize: none;
+  font-family: 'JetBrains Mono', monospace;
+  font-size: 14px;
+  line-height: 1.6;
+  outline: none;
+}
+
+.kb-textarea::placeholder {
+  color: var(--text-secondary);
+  opacity: 0.5;
+}
+</style>

web/src/components/Sidebar.vue

@@ -1,4 +1,5 @@
 <script setup lang="ts">
+import { ref } from 'vue'
 import type { Project } from '../types'
 
 defineProps<{
@@ -10,14 +11,22 @@ const emit = defineEmits<{
   select: [id: string]
   create: []
   delete: [id: string]
+  openKb: []
 }>()
 
+const showSettings = ref(false)
+
 function onDelete(e: Event, id: string) {
   e.stopPropagation()
   if (confirm('确定删除这个项目？')) {
     emit('delete', id)
   }
 }
+
+function onOpenKb() {
+  showSettings.value = false
+  emit('openKb')
+}
 </script>
 
 <template>
@@ -41,6 +50,14 @@ function onDelete(e: Event, id: string) {
         <span class="project-time">{{ new Date(project.updated_at).toLocaleDateString() }}</span>
       </div>
     </nav>
+    <div class="sidebar-footer">
+      <div class="settings-wrapper">
+        <button class="btn-settings" @click="showSettings = !showSettings">Settings</button>
+        <div v-if="showSettings" class="settings-menu">
+          <button class="settings-item" @click="onOpenKb">Knowledge Base</button>
+        </div>
+      </div>
+    </div>
   </aside>
 </template>
 
@@ -153,4 +170,59 @@ function onDelete(e: Event, id: string) {
   font-size: 11px;
   color: var(--text-secondary);
 }
+
+.sidebar-footer {
+  padding: 12px 16px;
+  border-top: 1px solid var(--border);
+}
+
+.settings-wrapper {
+  position: relative;
+}
+
+.btn-settings {
+  width: 100%;
+  padding: 8px;
+  background: transparent;
+  color: var(--text-secondary);
+  border: none;
+  font-size: 13px;
+  cursor: pointer;
+  text-align: left;
+  border-radius: 6px;
+}
+
+.btn-settings:hover {
+  background: var(--bg-tertiary);
+  color: var(--text-primary);
+}
+
+.settings-menu {
+  position: absolute;
+  bottom: 100%;
+  left: 0;
+  right: 0;
+  margin-bottom: 4px;
+  background: var(--bg-primary);
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  padding: 4px;
+  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
+}
+
+.settings-item {
+  width: 100%;
+  padding: 8px 12px;
+  background: none;
+  border: none;
+  color: var(--text-primary);
+  font-size: 13px;
+  text-align: left;
+  cursor: pointer;
+  border-radius: 6px;
+}
+
+.settings-item:hover {
+  background: var(--bg-tertiary);
+}
 </style>

web/src/components/WorkflowView.vue

@@ -82,7 +82,7 @@ function handleWsMessage(msg: WsMessage) {
       break
     case 'ReportReady':
       if (workflow.value && msg.workflow_id === workflow.value.id) {
-        workflow.value = { ...workflow.value, status: workflow.value.status }
+        loadData()
       }
       break
     case 'ProjectUpdate':