Retire mcp-csharp-create, mcp-csharp-test, and mcp-csharp-publish skills

[leslierichardson95]

What

Retires the remaining three mcp-csharp-* skills from the dotnet-ai plugin: mcp-csharp-create, mcp-csharp-test, and mcp-csharp-publish. Follows the cut of mcp-csharp-debug (#938) — this completes retirement of the family.

Why

Based on the cross-family skills-eval (#889) and the 30-day telemetry review (gist):

Skill	Eval (impact / families ✓)	Real demand
mcp-csharp-test	+0.65 but 0/5 families pass	2 users, 0 with ≥5 invocations
mcp-csharp-publish	+0.56 but 0/5 families pass	0 real users
mcp-csharp-create	0.40, wins only 2/5 (Sonnet, Haiku) and regresses both frontier models; avgN 2.6 (directional)	absent from telemetry report

None has demonstrated real demand. The only positive signal is a low-confidence eval that would require a full 5-family sweep to validate, with no usage to justify the investment. Retiring now (reversible via git history) is the pragmatic call over speculative strengthening.

Changes

• Delete plugins/dotnet-ai/skills/mcp-csharp-{create,test,publish}/ (SKILL.md + references)
• Delete tests/dotnet-ai/mcp-csharp-{create,test,publish}/ (eval.yaml)
• Remove the dotnet-ai CODEOWNERS block for the three skills and their tests
• Repoint the skill-validator doc example (InvestigatingResults.md) from the now-deleted mcp-csharp-create to a surviving skill (technology-selection)

dotnet-ai retains technology-selection. plugin.json auto-discovers ./skills/, so no manifest change is needed. Verified no remaining mcp-csharp-* references repo-wide (git grep). Rebased on main after #938 merged, so there are no conflicts with the debug cut.

Refs #889. Supersedes #939, #940, #941 (the earlier strengthen/fix PRs, now obsolete).

[github-actions]

Skill Coverage Report

	Plugin	Skill	Covered	Coverage
❔	dotnet-ai	mcp-csharp-create	—	error
❔	dotnet-ai	mcp-csharp-publish	—	error
❔	dotnet-ai	mcp-csharp-test	—	error

[Copilot]

Pull request overview

Retires the remaining mcp-csharp-* skills from the dotnet-ai plugin by removing their skill content and associated eval coverage, and updates repo documentation/ownership to match.

Changes:

• Removed the mcp-csharp-create, mcp-csharp-test, and mcp-csharp-publish skill directories (including reference docs).
• Removed the corresponding tests/dotnet-ai/mcp-csharp-*/eval.yaml evaluation files.
• Updated CODEOWNERS and the skill-validator “Investigating results” documentation to avoid referencing retired skills.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/dotnet-ai/mcp-csharp-test/eval.yaml	Removed eval coverage for the retired mcp-csharp-test skill.
tests/dotnet-ai/mcp-csharp-publish/eval.yaml	Removed eval coverage for the retired mcp-csharp-publish skill.
tests/dotnet-ai/mcp-csharp-create/eval.yaml	Removed eval coverage for the retired mcp-csharp-create skill.
plugins/dotnet-ai/skills/mcp-csharp-test/SKILL.md	Removed retired skill content.
plugins/dotnet-ai/skills/mcp-csharp-test/references/test-patterns.md	Removed retired skill reference material.
plugins/dotnet-ai/skills/mcp-csharp-test/references/evaluations.md	Removed retired skill reference material.
plugins/dotnet-ai/skills/mcp-csharp-publish/SKILL.md	Removed retired skill content.
plugins/dotnet-ai/skills/mcp-csharp-publish/references/nuget-packaging.md	Removed retired skill reference material.
plugins/dotnet-ai/skills/mcp-csharp-publish/references/mcp-registry.md	Removed retired skill reference material.
plugins/dotnet-ai/skills/mcp-csharp-publish/references/docker-azure.md	Removed retired skill reference material.
plugins/dotnet-ai/skills/mcp-csharp-create/SKILL.md	Removed retired skill content.
plugins/dotnet-ai/skills/mcp-csharp-create/references/transport-config.md	Removed retired skill reference material.
plugins/dotnet-ai/skills/mcp-csharp-create/references/api-patterns.md	Removed retired skill reference material.
eng/skill-validator/src/docs/InvestigatingResults.md	Updated example job name to reference a remaining skill (technology-selection).
.github/CODEOWNERS	Removed CODEOWNERS entries for the retired skills/tests.

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[AbhitejJohn]

Approving but tagging @luisquintanilla to take a look as well.

[AbhitejJohn]

@leslierichardson95 , @luisquintanilla : If this does get merged in leaving technology-selection as the only skill in this plugin, would it make sense to move that over to dotnet-advanced plugin? If we foresee more skills in this space in the near term, it would make sense to keep dotnet-ai around, otherwise it would be great to consolidate.