fix(tab-bar): prevent keyboard controller memory leak on rapid mount/unmount (#30906)

Issue number: resolves internal

---------

## What is the current behavior?
When `ion-tab-bar` is rapidly mounted and unmounted, a race condition in
connectedCallback can cause the keyboard controller to be created after
the component has been disconnected. This results in orphaned event
listeners (`keyboardWillShow`, `keyboardWillHide`) on the window object
that are never cleaned up, causing a memory leak.

## What is the new behavior?
The keyboard controller is now properly destroyed in all scenarios:
- If the component is disconnected while createKeyboardController is
pending, the promise is tracked and destroyed when it resolves
- If a new connectedCallback runs before the previous async completes,
the stale controller is destroyed

The promise tracking pattern ensures only the most recent async
operation assigns its result

## Does this introduce a breaking change?

- [ ] Yes
- [X] No

<!--
  If this introduces a breaking change:
1. Describe the impact and migration path for existing applications
below.
  2. Update the BREAKING.md file with the breaking change.
3. Add "BREAKING CHANGE: [...]" to the commit description when merging.
See
https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#footer
for more information.
-->


## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->
Current dev build:
```
8.7.17-dev.11767895575.16ea7cef
```

I was unable to find a way to create tests that accurately identified if
this problem was occurring. Memory leaks are notoriously difficult to
created automated tests for. I ultimately removed my previous attempts
because I didn't want to give a false sense of security.

Author: ShaneK

core/src/components/footer/footer.tsx

@@ -22,6 +22,7 @@ export class Footer implements ComponentInterface {
   private scrollEl?: HTMLElement;
   private contentScrollCallback?: () => void;
   private keyboardCtrl: KeyboardController | null = null;
+  private keyboardCtrlPromise: Promise<KeyboardController> | null = null;
 
   @State() private keyboardVisible = false;
 
@@ -52,7 +53,7 @@ export class Footer implements ComponentInterface {
   }
 
   async connectedCallback() {
-    this.keyboardCtrl = await createKeyboardController(async (keyboardOpen, waitForResize) => {
+    const promise = createKeyboardController(async (keyboardOpen, waitForResize) => {
       /**
        * If the keyboard is hiding, then we need to wait
        * for the webview to resize. Otherwise, the footer
@@ -64,11 +65,32 @@ export class Footer implements ComponentInterface {
 
       this.keyboardVisible = keyboardOpen; // trigger re-render by updating state
     });
+    this.keyboardCtrlPromise = promise;
+
+    const keyboardCtrl = await promise;
+
+    /**
+     * Only assign if this is still the current promise.
+     * Otherwise, a new connectedCallback has started or
+     * disconnectedCallback was called, so destroy this instance.
+     */
+    if (this.keyboardCtrlPromise === promise) {
+      this.keyboardCtrl = keyboardCtrl;
+      this.keyboardCtrlPromise = null;
+    } else {
+      keyboardCtrl.destroy();
+    }
   }
 
   disconnectedCallback() {
+    if (this.keyboardCtrlPromise) {
+      this.keyboardCtrlPromise.then((ctrl) => ctrl.destroy());
+      this.keyboardCtrlPromise = null;
+    }
+
     if (this.keyboardCtrl) {
       this.keyboardCtrl.destroy();
+      this.keyboardCtrl = null;
     }
   }
 

core/src/components/tab-bar/tab-bar.tsx

@@ -22,6 +22,7 @@ import type { TabBarChangedEventDetail } from './tab-bar-interface';
 })
 export class TabBar implements ComponentInterface {
   private keyboardCtrl: KeyboardController | null = null;
+  private keyboardCtrlPromise: Promise<KeyboardController> | null = null;
   private didLoad = false;
 
   @Element() el!: HTMLElement;
@@ -88,7 +89,7 @@ export class TabBar implements ComponentInterface {
   }
 
   async connectedCallback() {
-    this.keyboardCtrl = await createKeyboardController(async (keyboardOpen, waitForResize) => {
+    const promise = createKeyboardController(async (keyboardOpen, waitForResize) => {
       /**
        * If the keyboard is hiding, then we need to wait
        * for the webview to resize. Otherwise, the tab bar
@@ -100,11 +101,32 @@ export class TabBar implements ComponentInterface {
 
       this.keyboardVisible = keyboardOpen; // trigger re-render by updating state
     });
+    this.keyboardCtrlPromise = promise;
+
+    const keyboardCtrl = await promise;
+
+    /**
+     * Only assign if this is still the current promise.
+     * Otherwise, a new connectedCallback has started or
+     * disconnectedCallback was called, so destroy this instance.
+     */
+    if (this.keyboardCtrlPromise === promise) {
+      this.keyboardCtrl = keyboardCtrl;
+      this.keyboardCtrlPromise = null;
+    } else {
+      keyboardCtrl.destroy();
+    }
   }
 
   disconnectedCallback() {
+    if (this.keyboardCtrlPromise) {
+      this.keyboardCtrlPromise.then((ctrl) => ctrl.destroy());
+      this.keyboardCtrlPromise = null;
+    }
+
     if (this.keyboardCtrl) {
       this.keyboardCtrl.destroy();
+      this.keyboardCtrl = null;
     }
   }