fix: fix: transcribe audio before mention check in groups with requireMention (openclaw#9973) thanks @mcinteerj

Verified:
- pnpm install --frozen-lockfile
- pnpm build
- pnpm check
- pnpm test

Co-authored-by: mcinteerj <3613653+mcinteerj@users.noreply.github.com>

src/media-understanding/attachments.ts

@@ -182,6 +182,10 @@ export function selectAttachments(params: {
 }): MediaAttachment[] {
   const { capability, attachments, policy } = params;
   const matches = attachments.filter((item) => {
+    // Skip already-transcribed audio attachments from preflight
+    if (capability === "audio" && item.alreadyTranscribed) {
+      return false;
+    }
     if (capability === "image") {
       return isImageAttachment(item);
     }