Fix NuGet publish workflow output path

[liamgold]

Fixes the publish workflow to use the default dotnet pack output location (src/bin/Release/*.nupkg) instead of a custom ./nupkg directory that wasn't being created properly.

[Copilot]

Pull Request Overview

This PR fixes the NuGet package publishing workflow by correcting the output path for packaged files. The workflow was attempting to use a custom ./nupkg directory that wasn't being created, causing the publish step to fail.

Key changes:

• Removed the custom --output ./nupkg parameter from the pack command to use dotnet's default output location
• Updated the push command to reference the default pack output path at src/bin/Release/*.nupkg

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