feat(semantic-index): expose semantic search via routes, agent tool and pipeline

Add shared /_web/ai/semantic-index HTTP routes and wire the service into
CLI web and Electron internal API. Introduce the semantic_search_current_chat
agent tool (AGENT-only, not MCP) with desensitized output and a narrowed
service interface, forward the semantic-search context through the CLI and
Desktop tool adapters, and integrate on-demand semantic search into the
agent pipeline with guidance and a max-result-token evidence budget.

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/node-runtime/src/ai/agent/index.ts

@@ -6,6 +6,7 @@ export type { LlmRouteDecider, RequestRoute, RouteDecision, RouteDecisionSource,
 export { buildPlanGuidance, createAnalysisPlanner, createPlanContentBlock } from './planner'
 export { createDataSnapshotFromOverview } from './data-snapshot'
 export type { ChatOverviewForSnapshot } from './data-snapshot'
+export { buildSemanticSearchGuidance } from './semantic-search-guidance'
 export type {
   AnalysisPlanIntent,
   AnalysisPlanner,

packages/node-runtime/src/ai/agent/semantic-search-guidance.ts

@@ -0,0 +1,24 @@
+/**
+ * 语义检索工具引导语
+ *
+ * 仅当当前会话语义索引可检索、工具被暴露给 LLM 时，由两端 runner 注入 system prompt。
+ * 引导模型在需要历史证据时调用 semantic_search_current_chat，避免寒暄/写作类问题无谓检索。
+ */
+
+function isChinese(locale?: string): boolean {
+  return (locale ?? '').toLowerCase().startsWith('zh')
+}
+
+export function buildSemanticSearchGuidance(locale?: string): string {
+  if (isChinese(locale)) {
+    return [
+      '当需要确认本对话历史中的具体事实、人物、地点、事件或过往提及时，调用 semantic_search_current_chat 检索相关片段。',
+      '寒暄、写作、解释通用概念等不依赖历史证据的问题不要调用该工具。',
+    ].join('')
+  }
+  return [
+    'When you need concrete facts, people, places, events, or past mentions from THIS conversation history, ',
+    'call semantic_search_current_chat to retrieve relevant excerpts. ',
+    'Do not call it for greetings, writing, or explaining general concepts that need no historical evidence.',
+  ].join('')
+}

packages/node-runtime/src/services/adapters/database-manager-adapter.test.ts

@@ -17,6 +17,7 @@ function createPathProvider(root: string): PathProvider {
     getSystemDir: () => root,
     getUserDataDir: () => path.join(root, 'data'),
     getDatabaseDir: () => path.join(root, 'data', 'databases'),
+    getVectorDir: () => path.join(root, 'data', 'vector'),
     getAiDataDir: () => path.join(root, 'ai'),
     getSettingsDir: () => path.join(root, 'settings'),
     getCacheDir: () => path.join(root, 'cache'),