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/card/builder.ts

@@ -12,7 +12,7 @@
  */
 
 import type { ToolUseTraceStep } from "./trace-store.js";
-import type { CardContentSegment } from "../outboundImages.js";
+import { maskMarkdownImagesForStreaming, type CardContentSegment } from "../outboundImages.js";
 
 // ---------------------------------------------------------------------------
 // Types
@@ -411,6 +411,7 @@ function buildAnswerElements(
     let remaining = MAX_TEXT_LENGTH;
     for (const segment of contentSegments) {
       if (segment.type === "image") {
+        if (segment.imgKey.trim() === "") continue;
         elements.push({
           tag: "img",
           img_key: segment.imgKey,
@@ -421,9 +422,13 @@ function buildAnswerElements(
         continue;
       }
       if (segment.content === "" || remaining <= 0) continue;
-      const slice = segment.content.length <= remaining
-        ? segment.content
-        : truncateText(segment.content, remaining);
+      // Feishu card markdown rejects ![](url) without a Feishu image_key
+      // ("card contains images but no imagekey" / empty image key).
+      const safe = maskMarkdownImagesForStreaming(segment.content);
+      if (safe === "" || remaining <= 0) continue;
+      const slice = safe.length <= remaining
+        ? safe
+        : truncateText(safe, remaining);
       remaining -= slice.length;
       elements.push({
         tag: "markdown",
@@ -433,9 +438,11 @@ function buildAnswerElements(
     return elements;
   }
   if (text === "") return [];
+  const safe = maskMarkdownImagesForStreaming(text);
+  if (safe === "") return [];
   return [{
     tag: "markdown",
-    content: truncateText(text, MAX_TEXT_LENGTH),
+    content: truncateText(safe, MAX_TEXT_LENGTH),
   }];
 }