fix: preserve full calc-02 stack while limiting display to top 4

Keep the calculator stack unlimited in the demo and only constrain the rendered stack view. Also restore the edit cursor position when pulling a value into the input from the stack.

samples/calc-02/index.js

@@ -120,9 +120,7 @@ function clearStatus() {
 }
 
 function normalizeStack() {
-	while (calc.stack.length > 4) {
-		calc.stack.shift();
-	}
+	// Demo display only shows the top 4 stack values; the calculator stack remains unlimited.
 }
 
 function getStackLine(indexFromTop) {
@@ -159,7 +157,6 @@ function updateCopyButtons() {
 }
 
 function render() {
-	normalizeStack();
 	const isPortrait = window.matchMedia('(orientation: portrait)').matches || window.innerWidth <= 860;
 	calculatorEl?.classList.toggle('portrait', isPortrait);
 	calculatorEl?.classList.toggle('landscape', !isPortrait);
@@ -520,16 +517,18 @@ leftButton.addEventListener('click', () => {
 	}
 });
 downButton.addEventListener('click', () => {
-	if (!calc.isEditing && calc.isValidIndex(0)) {
-		const value = calc.stack[0];
-		calc.remove(0);
-		calc.isEditing = true;
-		calc.inputValue = calc.formatNumber(value);
-		render();
-		focusInput();
-	}
+if (!calc.isEditing && calc.isValidIndex(0)) {
+	const value = calc.stack[0];
+	calc.remove(0);
+	calc.isEditing = true;
+	calc.inputValue = calc.formatNumber(value);
+	editCursor = calc.inputValue.length;
+	render();
+	focusInput();
+}
 });
 
+
 rightButton.addEventListener('click', () => {
 	if (calc.isEditing) {
 		editCursor = Math.min(calc.inputValue.length, editCursor + 1);