feat(observability): 管理面板可观测性接真实数据——metrics/trace/audit 三端点 + 审计持久化

- observability.go/observability_metrics.go/observability_trace.go/observability_audit.go：
  拆分保证 ≤500行/函数≤80。metrics 并发安全 MetricsCollector(方法/路径/状态计数、平均/最大延迟、
  近1s QPS窗口)；trace 并发安全 RingBuffer(默认512, newest-first)+traceSink+MultiTraceWriter；
  audit AuditStore 接口+内存回退+SQLite 持久化(NewSQLiteAuditStore 参数化 SQL+audit_logs 表)。
- server.go：Deps.AuditStore + Server.obs + 3 路由 GET /admin/observability/{metrics,trace,audit}；
  ObserveSpan/TraceSink 注入点；middleware logging recordMetric；audit 落库(仅 slog→Append)。
- 前端 Obs.tsx：metrics 接 4 张真实 StatCard+请求分布、trace 接 span 列表(展开 props/events)、
  audit 从后端拉(前端内存审计作回退)；api.ts/types.ts 加 obs 端点/类型(AdminObservabilityMetrics/
  AdminTraceSpan/AuditRecord.id 放宽)。成本指标不伪造(保留'—'+注明)。
- wire.go 收口：Deps.AuditStore 注入 gateway.NewSQLiteAuditStore(ctx, a.db)(审计真落库)，
  未注入回退内存。
- Docs/api-client.md §2/v0.6。

实机验证：三端点 200，metrics 返回 totalRequests:4/qps:4/perPath/statusCounts:{200:4}。
go build/vet/test 全绿 + 前端 tsc。trace 数据源对接(gw.TraceSink→loop tracer)因 gw/tracer
构造顺序留作可选后置(端点已就绪, 未对接 span 空)。

frontend/web/src/lib/api.ts

@@ -3,11 +3,14 @@ import type {
   AdminChannelRecord,
   AdminIoTDevice,
   AdminLlmConfig,
+  AdminObservabilityMetrics,
   AdminPluginRecord,
   AdminRagHit,
   AdminRagResponse,
+  AdminTraceSpan,
   AdminUserRecord,
   ApiErrorShape,
+  AuditRecord,
   ChatSyncResult,
   LoginResult,
   MemoryRecord,
@@ -269,3 +272,21 @@ export function adminDeleteRag(id: string): Promise<{ id: string }> {
     body: JSON.stringify({ id }),
   });
 }
+
+/** GET /api/v1/admin/observability/metrics — gateway request metrics. */
+export function adminObservabilityMetrics(): Promise<AdminObservabilityMetrics> {
+  return request<AdminObservabilityMetrics>("/admin/observability/metrics");
+}
+/** GET /api/v1/admin/observability/trace?limit=N — most recent traced spans. */
+export function adminObservabilityTrace(limit?: number): Promise<AdminTraceSpan[]> {
+  return request<AdminTraceSpan[]>(`/admin/observability/trace${limitQuery(limit)}`);
+}
+/** GET /api/v1/admin/observability/audit?limit=N — most recent audit entries. */
+export function adminObservabilityAudit(limit?: number): Promise<AuditRecord[]> {
+  return request<AuditRecord[]>(`/admin/observability/audit${limitQuery(limit)}`);
+}
+
+/** Builds an optional ?limit=N query suffix (empty when no positive limit). */
+function limitQuery(limit?: number): string {
+  return limit && limit > 0 ? `?limit=${limit}` : "";
+}

frontend/web/src/lib/types.ts

@@ -274,15 +274,52 @@ export interface AdminRagResponse {
   hits?: AdminRagHit[];
 }
 
-/** One audit entry: who / what / when / result. */
+/** One audit entry: who / what / when / result. `id` is a string for the local
+ *  (client) trail but a number for backend-persisted entries. */
 export interface AuditRecord {
-  id: string;
+  id: string | number;
   who: string;
   what: string;
   when: string;
   result: string;
 }
 
+/** Gateway request metrics (GET /api/v1/admin/observability/metrics). Token/cost
+ *  is intentionally absent: the gateway does not track spend, and a fabricated
+ *  number would violate the "不伪造指标" red line. */
+export interface AdminObservabilityMetrics {
+  totalRequests: number;
+  qps: number;
+  avgLatencyMs: number;
+  maxLatencyMs: number;
+  perMethod: Record<string, number>;
+  perPath: Record<string, number>;
+  statusCounts: Record<string, number>;
+  llmCalls: number;
+  subagentEvents: number;
+}
+
+/** One traced span (GET /api/v1/admin/observability/trace). */
+export interface AdminTraceSpan {
+  id: string;
+  parentId?: string;
+  name: string;
+  kind: string;
+  status: string;
+  startedAt: string;
+  endedAt?: string;
+  durationNs: number;
+  props?: Record<string, unknown>;
+  events?: TraceEvent[];
+}
+
+/** A fine-grained event attached to a span. */
+export interface TraceEvent {
+  time: string;
+  type: string;
+  props?: Record<string, unknown>;
+}
+
 /** The owner profile (mirrors configs/users/owner.yaml). */
 export interface OwnerProfile {
   id: string;