System.Runtime.CompilerServices.Unsafe Assembly Loading Issue in Excel Add-in Environment

## Issue Description

When using `CommunityToolkit.Mvvm` version 8.4.0 in an Excel add-in built with Excel-DNA and .NET Framework 4.8, I encounter a persistent `System.IO.FileLoadException` when calling `WeakReferenceMessenger.Default.Register()`.

## Environment

- **CommunityToolkit.Mvvm**: 8.4.0
- **Target Framework**: .NET Framework 4.8
- **Platform**: Excel Add-in using Excel-DNA 1.8.0
- **Project Type**: SDK-style project (``)
- **OS**: Windows 10/11
- **Excel Version**: Microsoft Excel (Office 365)

## Error Details

### Exception Stack Trace
```
System.IO.FileLoadException: Could not load file or assembly 'System.Runtime.CompilerServices.Unsafe, Version=6.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
Source: CommunityToolkit.Mvvm
at CommunityToolkit.Mvvm.Messaging.WeakReferenceMessenger.Register[TMessage,TToken](Object recipient, TToken token, MessageHandlerDispatcher dispatcher)
at CommunityToolkit.Mvvm.Messaging.WeakReferenceMessenger.Register[TMessage,TToken](IRecipient`1 recipient, TToken token)
at CommunityToolkit.Mvvm.Messaging.IMessengerExtensions.Register[TMessage](IMessenger messenger, IRecipient`1 recipient)

Inner Exception:
FileLoadException: Could not load file or assembly 'System.Runtime.CompilerServices.Unsafe, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
```

### Key Observations
1. The outer exception expects `System.Runtime.CompilerServices.Unsafe` version **6.1.0.0**
2. The inner exception shows the runtime is actually trying to load version **6.0.0.0**
3. The correct version (6.1.0.0) is present in the output directory and verified via reflection
4. The issue only occurs in Excel add-in environment, not in regular applications

## Reproduction Code

### Project File (.csproj)
```xml

net48
true
true
true
true

```

### App.config
```xml

```

### Failing Code
```csharp
public class OrderManageViewModel
{
public OrderManageViewModel(IDataService data)
{
// This line throws the exception
WeakReferenceMessenger.Default.Register(this);
}
}
```

## What I've Tried

### 1. Verified Assembly Versions
- Confirmed `System.Runtime.CompilerServices.Unsafe.dll` version 6.1.0.0 is in the bin directory
- Used reflection to verify the assembly version matches expectations
- Checked that all related assemblies (`System.Memory`, `System.Buffers`) are correct versions

### 2. Assembly Binding Redirects
- Added comprehensive binding redirects in app.config
- Tried both auto-generated and manual binding redirects
- Verified redirects cover the full version range (0.0.0.0-6.1.0.0 → 6.1.0.0)

### 3. Custom Assembly Resolution
```csharp
// Tried multiple approaches including:
AppDomain.CurrentDomain.AssemblyResolve += (sender, args) => {
// Custom assembly loading logic
// Using Assembly.LoadFrom(), Assembly.LoadFile(), Assembly.Load(byte[])
};
```

### 4. Package Version Combinations
- Tried explicit references to `System.Runtime.CompilerServices.Unsafe` versions 6.0.0, 6.1.0
- Attempted downgrading CommunityToolkit.Mvvm to 8.2.2 (which expects 6.0.0)
- Verified package dependency chains

### 5. Excel-DNA Specific Solutions
- Tried configuring external libraries in .dna files
- Attempted various `CopyLocalLockFileAssemblies` and build settings

## Expected Behavior

`WeakReferenceMessenger.Default.Register()` should work without assembly loading exceptions, as it does in regular .NET applications.

## Actual Behavior

Consistent `FileLoadException` with version mismatch, despite correct assemblies being present and properly configured.

## Additional Context

### Build Output (showing correct resolution)
```
检测到包降级: System.Runtime.CompilerServices.Unsafe 从 6.1.0 降级到 6.0.0
Cyclone.ExcelToolkit -> CommunityToolkit.Mvvm 8.4.0 -> System.Runtime.CompilerServices.Unsafe (>= 6.1.0)
```

This suggests the build system correctly resolves to 6.1.0, but runtime loading fails.

### Excel Add-in Specific Context
This issue appears to be specific to Excel add-in environments where:
1. The CLR is hosted by Excel rather than being the primary application host
2. Assembly loading behavior may differ from standard .NET applications
3. Multiple AppDomains or assembly contexts might be involved

## Questions

1. **Is this a known issue** with CommunityToolkit.Mvvm in hosted CLR environments like Excel add-ins?

2. **Are there specific recommendations** for using CommunityToolkit.Mvvm in Excel-DNA or similar COM add-in scenarios?

3. **Could the library provide better error handling** or diagnostics for assembly loading issues?

4. **Is there a way to make CommunityToolkit.Mvvm more resilient** to version mismatches of System.Runtime.CompilerServices.Unsafe?

## Possible Solutions

Would any of these approaches be feasible for the library:

1. **Internal Assembly Resolution**: Could CommunityToolkit.Mvvm include its own assembly resolution logic for critical dependencies?

2. **Version Tolerance**: Could the library be more tolerant of minor version differences in System.Runtime.CompilerServices.Unsafe?

3. **Initialization Method**: Could there be an explicit initialization method that pre-loads dependencies before first use?

Thank you for this excellent library! Any guidance on resolving this Excel add-in compatibility issue would be greatly appreciated.