feat: add sender profile cache with LRU eviction

- SenderNameCache: TTL 10min, LRU max 2048 entries, getOrFetch pattern
- resolveSenderName: API call with cache integration
- Trigger uses cache for approval card resolutions and audit metadata
- Add unit tests (9) for cache lifecycle, LRU, expiry, and null handling

hub/src/feishu/client.ts

@@ -10,6 +10,7 @@ import { readFile, writeFile, mkdir } from "node:fs/promises";
 import { dirname } from "node:path";
 import type { FastifyBaseLogger } from "fastify";
 import { DEFAULT_MAX_MESSAGE_LENGTH, splitAtBoundary } from "./textStream.js";
+import type { SenderNameCache } from "./senderCache.js";
 
 export interface FeishuConfig {
   readonly appId: string;
@@ -95,6 +96,14 @@ export interface CardActionEvent {
   readonly token?: string;
 }
 
+type ContactUserResponse = {
+  readonly data?: {
+    readonly user?: {
+      readonly name?: string | undefined;
+    } | undefined;
+  } | undefined;
+} | null;
+
 // --- Message helpers ---
 
 export function buildOutboundPayload(content: string): OutboundPayload {
@@ -356,6 +365,35 @@ export async function removeReaction(rt: FeishuRuntime, messageId: string, react
   }
 }
 
+/** Resolve a Feishu sender display name from open_id, optionally using a cache. */
+export async function resolveSenderName(
+  rt: FeishuRuntime,
+  openId: string,
+  cache?: SenderNameCache,
+): Promise<string | null> {
+  if (openId === "") return null;
+
+  const fetchName = async (id: string): Promise<string | null> => {
+    try {
+      const res = await rt.client.request({
+        method: "GET",
+        url: `/open-apis/contact/v3/users/${encodeURIComponent(id)}`,
+        params: { user_id_type: "open_id" },
+      }) as ContactUserResponse;
+      const name = res?.data?.user?.name;
+      return typeof name === "string" && name !== "" ? name : null;
+    } catch (e) {
+      rt.logger.warn({ openId: id, err: e instanceof Error ? e.message : String(e) }, "resolveSenderName failed");
+      return null;
+    }
+  };
+
+  if (cache !== undefined) {
+    return cache.getOrFetch(openId, fetchName);
+  }
+  return fetchName(openId);
+}
+
 // --- File helpers ---
 
 /** Download a file/image from a Feishu message to a local path. */