Stabilize and unify some test skills

.github/CODEOWNERS

@@ -95,15 +95,14 @@
 /plugins/dotnet-experimental/plugin.json @JanKrivanek @ViktorHofer @Evangelink @ManishJayaswal @AbhitejJohn
 
 # dotnet-experimental-tests (everything experimental test related)
+/plugins/dotnet-experimental/skills/exp-dotnet-test-frameworks/ @dotnet/dotnet-testing
+
 /plugins/dotnet-experimental/skills/exp-test-tagging/ @dotnet/dotnet-testing
 /tests/dotnet-experimental/exp-test-tagging/ @dotnet/dotnet-testing
 
 /plugins/dotnet-experimental/skills/exp-test-maintainability/ @dotnet/dotnet-testing
 /tests/dotnet-experimental/exp-test-maintainability/ @dotnet/dotnet-testing
 
-/plugins/dotnet-experimental/skills/exp-test-boilerplate-detection/ @dotnet/dotnet-testing
-/tests/dotnet-experimental/exp-test-boilerplate-detection/ @dotnet/dotnet-testing
-
 /plugins/dotnet-experimental/skills/exp-assertion-quality/ @dotnet/dotnet-testing
 /tests/dotnet-experimental/exp-assertion-quality/ @dotnet/dotnet-testing
 

plugins/dotnet-experimental/skills/exp-assertion-quality/SKILL.md

@@ -46,7 +46,7 @@ Low assertion diversity signals shallow testing. Tests may pass while bugs hide
 
 ### Step 1: Gather the test code
 
-Read all test files the user provides. If the user points to a directory or project, scan for all test files (files containing `[TestClass]`, `[TestMethod]`, `[Fact]`, `[Test]`, or `[Theory]` attributes).
+Read all test files the user provides. If the user points to a directory or project, scan for all test files — see the `exp-dotnet-test-frameworks` skill for framework-specific markers.
 
 ### Step 2: Classify every assertion
 

plugins/dotnet-experimental/skills/exp-test-smell-detection/extensions/dotnet.md → plugins/dotnet-experimental/skills/exp-dotnet-test-frameworks/SKILL.md

@@ -1,4 +1,10 @@
-# .NET Extension
+---
+name: exp-dotnet-test-frameworks
+description: "Reference data for .NET test framework detection patterns, assertion APIs, skip annotations, setup/teardown methods, and common test smell indicators across MSTest, xUnit, NUnit, and TUnit. DO NOT USE directly — loaded by test analysis skills (exp-test-smell-detection, exp-assertion-quality, exp-test-maintainability, exp-test-tagging) when they need framework-specific lookup tables."
+user-invocable: false
+---
+
+# .NET Test Framework Reference
 
 Language-specific detection patterns for .NET test frameworks (MSTest, xUnit, NUnit, TUnit).