Add GitHub Action to check .NET 10 availability on Ubuntu runners

[Copilot]

Adds a workflow to determine if .NET 10 SDK is pre-installed on Ubuntu GitHub Action runners and whether it can be installed via actions/setup-dotnet@v4.

Workflow Features

• Pre-installation detection: Lists all installed .NET SDKs/runtimes and checks for .NET 10
• Installation validation: Attempts to install .NET 10 and verifies success
• Project creation test: Creates a net10.0 console app to validate full functionality
• Always-runs summary: Provides clear results regardless of .NET 10 availability

Triggers

• Manual via workflow_dispatch
• Push to main/develop
• Pull requests

Example Output

=== Checking for pre-installed .NET SDKs ===
✗ .NET 10 SDK is NOT pre-installed

=== Verifying .NET 10 after setup-dotnet ===
✓ .NET 10 SDK is now available!

All failure-prone steps use continue-on-error: true to ensure complete execution and reporting.

Original prompt

I want to know whether the Ubuntu Action runners already have .net10. Please create a PR with a simple action that check for this

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