fix(useBattery): handle unmount cleanup and promise rejection

  - Add mounted flag to prevent state updates after unmount
  - Prevent event listener registration if component unmounts before
    getBattery() resolves
  - Add .catch() handler to gracefully handle promise rejections
  - Fix misleading comment for fetched field

Author: samithahansaka

src/useBattery/index.ts

@@ -27,7 +27,7 @@ export type UseBatteryState = BatteryState & {
 	 */
 	isSupported: boolean;
 	/**
-	 * Whether the battery state is currently being fetched.
+	 * Whether the battery state has been fetched.
 	 */
 	fetched: boolean;
 };
@@ -96,15 +96,20 @@ export function useBattery(): UseBatteryState {
 		}
 
 		let battery: BatteryManager | null = null;
+		let mounted = true;
 
 		const handleChange = () => {
-			if (battery) {
+			if (battery && mounted) {
 				setState(getBatteryState(battery));
 			}
 		};
 
 		// eslint-disable-next-line @typescript-eslint/no-floating-promises,promise/catch-or-return,promise/prefer-await-to-then,promise/always-return
 		nav.getBattery().then((b) => {
+			if (!mounted) {
+				return;
+			}
+
 			battery = b;
 			setState(getBatteryState(battery));
 
@@ -115,6 +120,7 @@ export function useBattery(): UseBatteryState {
 		});
 
 		return () => {
+			mounted = false;
 			if (battery) {
 				off(battery, 'chargingchange', handleChange);
 				off(battery, 'chargingtimechange', handleChange);