Test new PR CI workflow

[valkyrienyanko]

Summary

• implement FOLLOW_UP item Borderless mode does not fully cover the entire screen (there is a 1 pixel border gap all around) #2 by adding IApplicationLifetime and replacing runtime Autoloads.Instance usage
• implement FOLLOW_UP item Pressing escape while in level.tscn while the hotkeys is open and currently waiting for new hotkey, escapes out of the hotkey menu back to the popup menu. This behaviour is undesired. Instead the first escape should cancel the waiting for hotkey input. Then the next escape should exit out of the options menu. #3 by removing ResourceOptionsSnapshot, exposing ResourceOptions via Settings, and removing obsolete options escape-hatches
• remove obsolete Game facade markers and migrate GameServicesLocator.Current.* call sites to Game.*
• add PR CI workflow for pull_request opened/synchronize/reopened that runs targeted format/build plus full build and tests
• update README service examples and recreate FOLLOW_UP.md with updated remaining item Roadmap #1 only

Validation

• dotnet format Template.sln --verify-no-changes
• dotnet build Template.sln
• dotnet test Template.PacketGen/PacketGen.Tests/PacketGen.Tests.csproj --no-build

This PR is also intended as a workflow trigger test for the new .github/workflows/pr_ci.yml workflow.