fix: replace deprecated path() with curve() in borrow arrows

Typst deprecated the path() function in favor of curve(). Updated the
borrowing hints arrow rendering to use curve() to eliminate deprecation
warnings during compilation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/app/create/worksheets/typstHelpers/subtraction/borrowBoxes.ts

@@ -75,7 +75,7 @@ export function generateBorrowBoxesRow(cellDimensions: CellDimensions): string {
                 top + left,
                 dx: ${arrowStartDx}in,
                 dy: ${arrowStartDy}in,
-                path(
+                curve(
                   stroke: (paint: gray.darken(30%), thickness: ${TYPST_CONSTANTS.ARROW_STROKE_WIDTH}pt),
                   // Start vertex (near the "1" in borrow box)
                   (0pt, 0pt),