fix(config): use truncateUtf16Safe for allowed-values hint text (#102512)

* fix(config): use truncateUtf16Safe for allowed-values hint text

Replace naive .slice(0, N) with truncateUtf16Safe() to prevent
surrogate pair splitting in config validation hint messages
shown to users.

Co-Authored-By: Claude <noreply@anthropic.com>

* test(config): prove UTF-16 allowed-value hint boundary

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/config/allowed-values.test.ts

@@ -23,6 +23,17 @@ describe("summarizeAllowedValues", () => {
     });
   });
 
+  it("counts the omitted UTF-16 units after preserving a surrogate pair", () => {
+    const prefix = "a".repeat(159);
+    const value = `${prefix}😀tail`;
+
+    expect(summarizeAllowedValues([value])).toStrictEqual({
+      formatted: `"${prefix}... (+6 chars)"`,
+      hiddenCount: 0,
+      values: [value],
+    });
+  });
+
   it("returns empty label for undefined allowed value", () => {
     const summary = summarizeAllowedValues([undefined]);
     expect(summary).toStrictEqual({

src/config/allowed-values.ts

@@ -1,5 +1,6 @@
 // Defines allowed-value metadata for config validation and docs.
 import { normalizeLowercaseStringOrEmpty } from "@openclaw/normalization-core/string-coerce";
+import { truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 
 const MAX_ALLOWED_VALUES_HINT = 12;
 const MAX_ALLOWED_VALUE_CHARS = 160;
@@ -14,7 +15,8 @@ function truncateHintText(text: string, limit: number): string {
   if (text.length <= limit) {
     return text;
   }
-  return `${text.slice(0, limit)}... (+${text.length - limit} chars)`;
+  const truncated = truncateUtf16Safe(text, limit);
+  return `${truncated}... (+${text.length - truncated.length} chars)`;
 }
 
 function safeStringify(value: unknown): string {