fix(calc-02): restore edited value on cancel

Canceling stack-top editing now pushes the original value back before
leaving edit mode, including Escape and ArrowDown handling.

samples/calc-02/index.js

@@ -95,6 +95,7 @@ function focusInput() {
 
 let statusTimer = null;
 let editCursor = 0;
+let editRestoreValue = null;
 
 function setStatus(message, isError = false, timeoutMs = 1400) {
 	if (!statusLine) return;
@@ -173,6 +174,14 @@ function stopEditing(clearValue = false) {
 	editCursor = 0;
 }
 
+function cancelEditing() {
+	if (editRestoreValue !== null) {
+		calc.push(editRestoreValue);
+	}
+	editRestoreValue = null;
+	stopEditing(true);
+}
+
 function moveEditCursor(delta) {
 	editCursor = Math.max(0, Math.min(calc.inputValue.length, editCursor + delta));
 }
@@ -182,6 +191,7 @@ function pushEditingValueIfNeeded() {
 	if (calc.inputValue !== '') {
 		calc.push(calc.parseInputValue(calc.inputValue));
 	}
+	editRestoreValue = null;
 	calc.inputValue = '';
 	calc.isEditing = false;
 	editCursor = 0;
@@ -190,6 +200,7 @@ function pushEditingValueIfNeeded() {
 function startEditingFromStackTop() {
 	if (!calc.isValidIndex(0)) return false;
 	const value = calc.stack[0];
+	editRestoreValue = value;
 	calc.remove(0);
 	calc.isEditing = true;
 	calc.inputValue = calc.formatNumber(value);
@@ -247,7 +258,7 @@ function execute(name) {
 			calc.clear();
 			stopEditing(true);
 		} else if (name === 'escape') {
-			stopEditing(true);
+			cancelEditing();
 		} else if (name === 'backspace') {
 			if (calc.isEditing) {
 				inputToX('Backspace');
@@ -383,6 +394,11 @@ function handleKeyboard(event) {
 	}
 	if (key === 'ArrowDown') {
 		event.preventDefault();
+		if (calc.isEditing) {
+			cancelEditing();
+			render();
+			return;
+		}
 		downButton.click();
 		return;
 	}
@@ -543,6 +559,7 @@ downButton.addEventListener('click', () => {
 });
 
 
+
 rightButton.addEventListener('click', () => {
 	if (calc.isEditing) {
 		moveEditCursor(1);