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/fileDeliveryTool.ts

@@ -296,7 +296,8 @@ function mcpInstructions(enabledTools: ReadonlySet<CphHubMcpToolId>): string {
   const instructions: string[] = [];
   if (enabledTools.has("send_file")) {
     instructions.push(
-      "Use send_file when the user asks to receive, resend, download, or attach a file.",
+      "Use send_file only for downloadable attachments the user should save (PDF, DOCX, ZIP, etc.).",
+      "For inline 图文 answers, put ![alt](workspace-relative-path) in the final assistant text instead of send_file; the hub embeds those images in the reply card.",
       "Do not claim a file was sent unless send_file returns success.",
       "If a generated file path is uncertain, list or inspect the workspace first, then call send_file with the actual path.",
     );