Fix flicker issues by ensuring all actively changing content fits in the viewport (#1217)

packages/cli/src/ui/utils/textUtils.ts

@@ -45,3 +45,25 @@ export function isBinary(
   // If no NULL bytes were found in the sample, we assume it's text.
   return false;
 }
+
+/*
+ * -------------------------------------------------------------------------
+ *  Unicode‑aware helpers (work at the code‑point level rather than UTF‑16
+ *  code units so that surrogate‑pair emoji count as one "column".)
+ * ---------------------------------------------------------------------- */
+
+export function toCodePoints(str: string): string[] {
+  // [...str] or Array.from both iterate by UTF‑32 code point, handling
+  // surrogate pairs correctly.
+  return Array.from(str);
+}
+
+export function cpLen(str: string): number {
+  return toCodePoints(str).length;
+}
+
+export function cpSlice(str: string, start: number, end?: number): string {
+  // Slice by code‑point indices and re‑join.
+  const arr = toCodePoints(str).slice(start, end);
+  return arr.join('');
+}