This section details on the original issue you should resolve

<issue_title>StorageFile.Local.OpenStreamAsync always use File.Open instead of the FileAccessMode argument</issue_title>
<issue_description>### Current behavior 🐛

FileNotFoundException thrown when trying to write new StorageFile in a Skia.Desktop Mac app.

Expected behavior 🎯

No exception thrown with correct entitlements or choice of output folder

How to reproduce it (as minimally and precisely as possible) 🔬

Demo project: https://github.com/baskren/MacDesktop_StorageFile_Write

Relevant configurations:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
	<dict>
		<key>com.apple.security.cs.allow-jit</key>
		<true/>
		<key>com.apple.security.files.user-selected.read-write</key>
		<true/>
		<key>com.apple.security.files.downloads</key>
		<true/>
		<key>com.apple.security.files.documents</key>
		<true/>
	</dict>
</plist>

• Tried adding either/or/both of the following to the project's .csproj, in the <Properties> group:

<CodesignEntitlements Condition=" $(TargetFramework.Contains('desktop')) " >Platforms/Desktop/MacOS/entitlements.plist</CodesignEntitlements>

<UnoMacOSEntitlements Condition=" $(TargetFramework.Contains('desktop')) " >Platforms/Desktop/MacOS/entitlements.plist</UnoMacOSEntitlements>

Workaround 🛠️

None known at this time

Renderer 🎨

• Skia
• Native

Affected platforms 📱💻🖥️

Desktop (macOS)

Uno.Sdk version (and other relevant versions) 📦

Uno.Sdk: 6.1.23

UnoFeatures:

• CSharpMarkup;
• Lottie;
• Hosting;
• Toolkit;
• Configuration;
• Localization;
• ThemeService;
• SkiaRenderer;

IDE version 🧑‍💻

Anything else we need to know? 💬

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

However that's not the problem. Entitlements are only needed if/when the app is packaged as an app bundle (and in the case of this entitlement the app would have to be sandboxed to need this).

For a dotnet app the file system is accessible with the same permission that the current user (launching the app) has.

The full exception is:

   at Interop.ThrowExceptionForIoErrno(ErrorInfo errorInfo, String path, Boolean isDirError)
   at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, UnixFileMode openPermissions, Int64& fileLength, UnixFileMode& filePermissions, Boolean failForSymlink, Boolean& wasSymlink, Func`4 createOpenException)
   at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
   at System.IO.File.Open(String path, FileMode mode, FileAccess access, FileShare share)
   at Windows.Storage.StorageFile.Local.OpenStreamAsync(CancellationToken ct, FileAccessMode accessMode, StorageOpenOptions options) in C:\a\1\s\src\Uno.UWP\Storage\StorageFile.Local.cs:line 43
   at Windows.Storage.StorageFile.OpenStream(CancellationToken ct, FileAccessMode accessMode, StorageOpenOption...

</details>

Fixes unoplatform/uno#21311

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