fix(hub): strip card markdown images + prefer inline ![] over send_file

Feishu interactive markdown rejects ![](http...) without image_key
(error 230099 empty/missing imagekey). Always mask residual image md in
card builders; skip img tags with empty keys; skip inline-code examples;
fetch remote images with a browser UA and without env HTTP_PROXY.
Steer the agent: use ![alt](workspace-path) for 图文, send_file only for
downloadable attachments.

Release v0.0.37.

hub/src/feishu/trigger.ts

@@ -1834,8 +1834,9 @@ async function senderAuditMetadata(rt: FeishuRuntime, openId: string): Promise<P
 function withFileDeliveryInstructions(systemPrompt: string | undefined, roleTools: readonly string[] | undefined): string | undefined {
   if (!roleToolsAllow(roleTools, "send_file")) return systemPrompt;
   const fileDeliveryPrompt =
-    "When the user asks you to send, resend, attach, or provide a file, call the cph_hub send_file tool with the actual existing file path. " +
-    "Do not say a file is attached or sent unless that tool returns success.";
+    "When the user asks for a downloadable file attachment (PDF/DOCX/ZIP/etc.), call the cph_hub send_file tool with the actual existing file path. " +
+    "Do not say a file is attached or sent unless that tool returns success. " +
+    "For 图文并茂 / inline illustrations inside your answer, do NOT use send_file. Put workspace-relative images in the final answer with markdown image syntax ![alt](relative/path.png) (or a public https image URL). The platform uploads those into the Feishu card. Prefer workspace files over remote URLs.";
   return systemPrompt === undefined ? fileDeliveryPrompt : `${systemPrompt}\n\n${fileDeliveryPrompt}`;
 }