fix(tui): mapped empty-string ellipsis argument to Ellipsis.Omit

- Updated truncateToWidth to map a string ellipsis of "" to Ellipsis.Omit.
- Added a regression test for issue #848 to verify empty-string ellipsis produces a plain truncation result.

packages/tui/src/utils.ts

@@ -28,7 +28,17 @@ export function truncateToWidth(
 	// and `maxWidth` is a required `u32` that throws on `null`/`undefined`
 	// everywhere. Pass concrete defaults that mirror the Rust `unwrap_or`s.
 	const safeWidth = Number.isFinite(maxWidth) ? Math.max(0, Math.trunc(maxWidth)) : 0;
-	return nativeTruncateToWidth(text, safeWidth, ellipsisKind ?? Ellipsis.Unicode, pad ?? false, getDefaultTabWidth());
+	let resolvedEllipsis: Ellipsis | null | undefined | string = ellipsisKind;
+	if (typeof resolvedEllipsis === "string") {
+		resolvedEllipsis = resolvedEllipsis === "" ? Ellipsis.Omit : Ellipsis.Unicode;
+	}
+	return nativeTruncateToWidth(
+		text,
+		safeWidth,
+		resolvedEllipsis ?? Ellipsis.Unicode,
+		pad ?? false,
+		getDefaultTabWidth(),
+	);
 }
 
 export function wrapTextWithAnsi(text: string, width: number): string[] {

packages/tui/test/issue-848-repro.test.ts

@@ -26,6 +26,10 @@ describe("issue #848: truncateToWidth wrapper rejects nullish napi inputs", () =
 		expect(result).toBe("hello world");
 	});
 
+	it("maps a legacy empty-string ellipsis argument to omit ellipsis", () => {
+		const result = truncateToWidth("hello world", 5, "" as unknown as Parameters<typeof truncateToWidth>[2]);
+		expect(result).toBe("hello");
+	});
 	it("returns a string when ellipsisKind / pad are undefined", () => {
 		const result = truncateToWidth("hello world", 80, undefined, undefined);
 		expect(typeof result).toBe("string");