Rename IsCopilotCli to IsCopilot in AiCliDetector

Renames the IsCopilotCli property to IsCopilot and updates its detection logic to use the GITHUB_COPILOT_RUNTIME environment variable instead of GITHUB_COPILOT_CLI. Updates all references and documentation accordingly.

Author: SimonCropp

readme.md

@@ -177,7 +177,7 @@ There are also individual properties to check for each specific AI CLI
 <!-- snippet: AiCliDetectorProps -->
 <a id='snippet-AiCliDetectorProps'></a>
 ```cs
-var isCopilotCli = AiCliDetector.IsCopilotCli;
+var isCopilot = AiCliDetector.IsCopilot;
 var isAider = AiCliDetector.IsAider;
 var isClaudeCode = AiCliDetector.IsClaudeCode;
 ```

src/DiffEngine.Tests/AiCliDetectorTest.cs

@@ -8,12 +8,13 @@ public void Props()
 
         #region AiCliDetectorProps
 
-        var isCopilotCli = AiCliDetector.IsCopilotCli;
+        var isCopilot = AiCliDetector.IsCopilot;
         var isAider = AiCliDetector.IsAider;
         var isClaudeCode = AiCliDetector.IsClaudeCode;
 
         #endregion
 
+        Assert.True(isCopilot);
         // ReSharper restore UnusedVariable
     }
 }

src/DiffEngine/AiCliDetector.cs

@@ -5,10 +5,10 @@ public static class AiCliDetector
     static AiCliDetector()
     {
         var variables = Environment.GetEnvironmentVariables();
-        
-        // GitHub Copilot CLI
+
+        // GitHub Copilot
         // https://docs.github.com/en/copilot/using-github-copilot/using-github-copilot-in-the-command-line
-        IsCopilotCli = variables.Contains("GITHUB_COPILOT_CLI");
+        IsCopilot = variables.Contains("GITHUB_COPILOT_RUNTIME");
 
         // Aider
         // https://aider.chat/docs/config/dotenv.html
@@ -18,12 +18,12 @@ static AiCliDetector()
         // https://docs.anthropic.com/en/docs/build-with-claude/claude-cli
         IsClaudeCode = variables.Contains("CLAUDE_CODE") || variables.Contains("ANTHROPIC_CLI");
 
-        Detected = IsCopilotCli ||
+        Detected = IsCopilot ||
                    IsAider ||
                    IsClaudeCode;
     }
 
-    public static bool IsCopilotCli { get; }
+    public static bool IsCopilot { get; }
 
     public static bool IsAider { get; }