Add sf-tui shared utility functions.

Provides rightAlign helper for text alignment in terminal UI.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/resources/extensions/sf-tui/shared.ts

@@ -0,0 +1,8 @@
+import { visibleWidth } from "@sf-run/pi-tui";
+
+export function rightAlign(left: string, right: string, width: number): string {
+  const leftVis = visibleWidth(left);
+  const rightVis = visibleWidth(right);
+  const gap = Math.max(1, width - leftVis - rightVis);
+  return left + " ".repeat(gap) + right;
+}