Serialize .NET main workflow runs

[aaronpowell]

Closes: N/A (no relevant issue)

Serialize runs of the .NET main workflow by ref and cancel an in-progress run when a newer run for that ref starts. This prevents overlapping main-branch runs while ensuring the latest run proceeds.

PR Checklist

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• PR doesn't include merge commits (always rebase on top of our main, if needed)
• New integration
  • Docs are written
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Every new API (including internal ones) has full XML docs
• Code follows all style conventions

Other information

• No relevant issue exists; the repository template requires an issue link, so this PR is submitted without one.
• Validation: parsed the modified workflow YAML; git diff --check passed.

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/CommunityToolkit/Aspire/main/eng/scripts/dogfood-pr.sh | bash -s -- 1984

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/CommunityToolkit/Aspire/main/eng/scripts/dogfood-pr.ps1) } 1984"

[Copilot]

Copilot review overview

🟢 Approval recommended

No unresolved review issues remain.

Review effort: Lite
Findings: None

What changed in this PR

Adds GitHub Actions concurrency control to serialize .NET main workflow runs per ref and cancel older runs.

Changes:

• Groups runs by workflow and Git ref.
• Cancels in-progress runs when a newer run starts.

File	Description
.github/​workflows/​dotnet-main.yml	Adds workflow-level concurrency settings.

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