Add dotnet/skills marketplace and enable plugins

[Evangelink]

Add .github/copilot/settings.json to configure Copilot agent plugin marketplaces and enable dotnet plugins:

• dotnet/arcade-skills marketplace with dotnet-dnceng plugin
• dotnet/skills marketplace with dotnet, dotnet-msbuild, dotnet-nuget, and dotnet-test plugins

Relates to (and should replace a big part of) #13574

[Copilot]

Pull request overview

Adds a GitHub Copilot agent configuration file to register additional plugin marketplaces and enable a set of dotnet-related plugins for this repo.

Changes:

• Add .github/copilot/settings.json defining two extra marketplaces (dotnet/arcade-skills, dotnet/skills)
• Enable dotnet-dnceng, dotnet, dotnet-msbuild, dotnet-nuget, and dotnet-test plugins from those marketplaces

Show a summary per file

File	Description
.github/copilot/settings.json	Registers dotnet plugin marketplaces and enables selected dotnet plugins for Copilot agents

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0

[github-actions]

24-Dimension Expert Review — .github/copilot/settings.json

PR #13582 adds a Copilot agent configuration file that registers two plugin marketplaces and enables 5 plugins. This is a purely additive, non-code configuration change.

Verification Performed

• ✅ dotnet/arcade-skills — confirmed official dotnet org repo, contains plugins/dotnet-dnceng
• ✅ dotnet/skills — confirmed official dotnet org repo (1,341 ★), contains plugins/dotnet, plugins/dotnet-msbuild, plugins/dotnet-nuget, plugins/dotnet-test
• ✅ JSON is well-formed
• ✅ PR references related work (#13574)

Dimension Summary

#	Dimension	Verdict	Notes
1	Backwards Compatibility	✅ LGTM	New file, purely additive
2	ChangeWave Discipline	✅ LGTM	N/A — no engine behavioral change
3	Performance & Allocation	✅ LGTM	N/A — no runtime code
4	Test Coverage	✅ LGTM	N/A — config file, no testable behavior
5	Error Message Quality	✅ LGTM	N/A — no error messages
6	Logging & Diagnostics	✅ LGTM	N/A — no logging
7	String Comparison	✅ LGTM	N/A — no C# code
8	API Surface	✅ LGTM	N/A — no API changes
9	Target Authoring	✅ LGTM	N/A — no targets
10	Design Before Implementation	✅ LGTM	Simple config, well-scoped
11	Cross-Platform	✅ LGTM	N/A — JSON file
12	Code Simplification	✅ LGTM	N/A — no code
13	Concurrency	✅ LGTM	N/A — no runtime code
14	Naming Precision	✅ LGTM	Plugin names follow dotnet conventions
15	SDK Integration	✅ LGTM	N/A — no SDK changes
16	Idiomatic C# Patterns	✅ LGTM	N/A — no C# code
17	File I/O & Path Handling	✅ LGTM	N/A — no file I/O
18	Documentation Accuracy	✅ LGTM	Config file, no doc update needed
19	Build Infrastructure	✅ LGTM	Does not affect build pipeline
20	Scope & PR Discipline	✅ LGTM	Single focused change, references #13574
21	Evaluation Model	✅ LGTM	N/A — no evaluation changes
22	Correctness & Edge Cases	✅ LGTM	All 5 plugin names verified to exist
23	Dependency Management	✅ LGTM	References trusted dotnet org repos only
24	Security Awareness	✅ LGTM	Both repos are official dotnet org, MIT-licensed

Result: 24/24 dimensions clear. No issues found.

Generated by Expert Code Review (on open) for issue #13582 · ● 2.3M

[jankratochvilcz]

Thanks for the PR, let's discuss on the one comment and then merge!

[Evangelink]

@jankratochvilcz done

[jankratochvilcz]

Thanks, approving!