fix(whatsapp): elide auto-reply text on UTF-16 boundary (#96580)

elide truncated text with String.slice(0, limit) on a UTF-16 code-unit
index, so an astral character straddling the limit was cut into a lone
surrogate; the truncated-char count was also computed from the fixed
limit rather than the actual kept length.

Truncate with truncateUtf16Safe so a surrogate pair is never split, and
derive the truncated-char count from the kept length so the annotation
stays accurate.

Adds tests asserting no lone surrogate when the limit lands inside an
emoji and that a complete astral character is kept when it fits.

extensions/whatsapp/src/auto-reply/util.ts

@@ -1,5 +1,6 @@
 // Whatsapp plugin module implements util behavior.
 import { normalizeLowercaseStringOrEmpty } from "openclaw/plugin-sdk/string-coerce-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 
 export function elide(text?: string, limit = 400) {
   if (!text) {
@@ -8,7 +9,8 @@ export function elide(text?: string, limit = 400) {
   if (text.length <= limit) {
     return text;
   }
-  return `${text.slice(0, limit)}… (truncated ${text.length - limit} chars)`;
+  const truncated = truncateUtf16Safe(text, limit);
+  return `${truncated}… (truncated ${text.length - truncated.length} chars)`;
 }
 
 export function markWhatsAppVisibleDeliveryError(error: unknown): unknown {

extensions/whatsapp/src/auto-reply/web-auto-reply-utils.test.ts

@@ -365,6 +365,15 @@ describe("web auto-reply util", () => {
   });
 
   describe("elide", () => {
+    const hasLoneSurrogate = (value: string): boolean =>
+      Array.from(value).some((char) => {
+        if (char.length !== 1) {
+          return false;
+        }
+        const codeUnit = char.charCodeAt(0);
+        return codeUnit >= 0xd800 && codeUnit <= 0xdfff;
+      });
+
     it("returns undefined for undefined input", () => {
       expect(elide(undefined)).toBe(undefined);
     });
@@ -376,6 +385,20 @@ describe("web auto-reply util", () => {
     it("truncates and annotates when over limit", () => {
       expect(elide("abcdef", 3)).toBe("abc… (truncated 3 chars)");
     });
+
+    it("does not split surrogate pairs when the limit lands inside an emoji", () => {
+      const output = elide("😀😀😀", 5);
+
+      expect(output).toBe("😀😀… (truncated 2 chars)");
+      expect(hasLoneSurrogate(output ?? "")).toBe(false);
+    });
+
+    it("keeps a complete astral character when it fits before the limit", () => {
+      const output = elide("ab😀cd", 4);
+
+      expect(output).toBe("ab😀… (truncated 2 chars)");
+      expect(hasLoneSurrogate(output ?? "")).toBe(false);
+    });
   });
 
   describe("isLikelyWhatsAppCryptoError", () => {