[FKA]Slider cannot be focused using Tab key with Full Keyboard Access enabled

### Steps to reproduce

1. Clone the a11y assessments app from flutter repo and build the app in iPad/iPhone
2. Enable Full Keyboard Access on the iPad.
3. Connect a physical keyboard.
4. Launch the application.
5. Navigate to the screen containing the Slider control.
6. Place keyboard focus on the first interactive element.
7. Press the Tab key repeatedly to navigate through the interactive elements.
8. Observe the behavior when navigation reaches the Slider.

### Expected results

The Slider should receive keyboard focus when navigating sequentially using the Tab key.

A visible focus highlight should be displayed around/on the Slider so that the user can identify that the Slider currently has focus.

### Actual results

The Slider is skipped during Tab navigation and does not receive a visible focus highlight.

As a result, the Slider cannot be identified or accessed through sequential keyboard navigation.

### Code sample

Code sample

```dart
[Paste your code here]
```

### Screenshots or Video

Screenshots / Video demonstration

https://github.com/user-attachments/assets/c8f8bf6a-fa87-45c5-bafd-b6c5a734dcb5

### Logs

Logs

```console
[Paste your logs here]
```

### Flutter Doctor output

Doctor output

```console
[✓] Flutter (Channel master, 3.48.0-1.0.pre-524, on macOS 27.0 26A5421a darwin-arm64, locale en-US) [1,364ms]
• Flutter version 3.48.0-1.0.pre-524 on channel master at /Users/preethikandukuri/development/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision f5f6313e8c (4 hours ago), 2026-08-31 05:22:09 +0000
• Engine revision f5f6313e8c
• Dart version 3.14.0 (build 3.14.0-180.0.dev)
• DevTools version 2.61.0-dev.0
• Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android,
enable-ios, cli-animations, enable-native-assets, enable-record-use, enable-swift-package-manager,
omit-legacy-version-file, enable-lldb-debugging, enable-uiscene-migration, enable-riscv64, enable-hcpp

[✓] Android toolchain - develop for Android devices (Android SDK version 37.0.0) [455ms]
• Android SDK at /Users/preethikandukuri/Library/Android/sdk
• Emulator version 37.1.11.0 (build_id 15917651) (CL:N/A)
• Platform android-37.0, build-tools 37.0.0
• ANDROID_HOME = /Users/preethikandukuri/Library/Android/sdk
• Java binary at: /Applications/Android Studio RC.app/Contents/jbr/Contents/Home/bin/java
This JDK is specified in your Flutter configuration.
To change the current JDK, run: `flutter config --jdk-dir="path/to/jdk"`.
• Java version OpenJDK Runtime Environment (build 25.0.3+-15898627-b508.16)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 27.0) [657ms]
• Xcode at /Applications/Xcode-beta276.app/Contents/Developer
• Build 27A5252f
• CocoaPods version 1.16.2

[✓] Chrome - develop for the web [4ms]
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (5 available) [6.0s]
• sdk gphone16k arm64 (mobile) • emulator-5554 • android-arm64 • Android 17 (API 37)
(emulator)
• iPad (wireless) (mobile) • 00008122-001A08DC22B9801C • ios • iOS 27.0 24A5424a
• iPhone 17 Pro (mobile) • 6A22C9A6-0DD2-4ADA-84BB-ECB0DDE39E6C • ios •
com.apple.CoreSimulator.SimRuntime.iOS-27-0 (simulator)
• macOS (desktop) • macos • darwin-arm64 • macOS 27.0 26A5421a
darwin-arm64
• Chrome (web) • chrome • web-javascript • Google Chrome 152.0.7977.65

[✓] Network resources [893ms]
• All expected network resources are available.

```