fix: use Copilot launch command for version checks

Run the Copilot CLI version probe through the resolved launch path and args instead of invoking the Windows shim directly. This keeps the version check aligned with the SDK launch strategy and avoids false 'Version unknown' results from the Winget-installed Copilot executable.

Add a regression test covering the constructed launch command.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

sidecar/src/Kopaya.AgentHost/Services/CopilotConnectionMetadataResolver.cs

@@ -32,9 +32,10 @@ internal static partial class CopilotConnectionMetadataResolver
     {
         try
         {
+            (string executablePath, string[] arguments) = CreateCliCommand(cliContext, "version");
             CommandResult result = await RunProcessAsync(
-                executablePath: cliContext.CliPath,
-                arguments: ["version"],
+                executablePath: executablePath,
+                arguments: arguments,
                 environment: cliContext.Environment,
                 timeout: CopilotVersionTimeout,
                 cancellationToken).ConfigureAwait(false);
@@ -59,6 +60,18 @@ internal static partial class CopilotConnectionMetadataResolver
         }
     }
 
+    internal static (string ExecutablePath, string[] Arguments) CreateCliCommand(
+        CopilotCliContext cliContext,
+        params string[] arguments)
+    {
+        ArgumentNullException.ThrowIfNull(cliContext);
+        ArgumentNullException.ThrowIfNull(arguments);
+
+        return (
+            cliContext.LaunchPath,
+            [.. cliContext.LaunchArgs, .. arguments]);
+    }
+
     internal static SidecarCopilotCliVersionDiagnosticsDto ParseCliVersionOutput(
         string? standardOutput,
         string? standardError = null,

sidecar/tests/Kopaya.AgentHost.Tests/CopilotConnectionMetadataResolverTests.cs

@@ -36,6 +36,22 @@ public sealed class CopilotConnectionMetadataResolverTests
         Assert.Equal("1.0.10", diagnostics.LatestVersion);
     }
 
+    [Fact]
+    public void CreateCliCommand_UsesLaunchPathAndAppendsCommandArguments()
+    {
+        CopilotCliContext cliContext = new(
+            CliPath: @"C:\tools\copilot.exe",
+            LaunchPath: @"C:\Windows\System32\cmd.exe",
+            LaunchArgs: ["/d", "/s", "/c", "copilot"],
+            Environment: new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase));
+
+        (string executablePath, string[] arguments) =
+            CopilotConnectionMetadataResolver.CreateCliCommand(cliContext, "version");
+
+        Assert.Equal(@"C:\Windows\System32\cmd.exe", executablePath);
+        Assert.Equal(["/d", "/s", "/c", "copilot", "version"], arguments);
+    }
+
     [Fact]
     public void NormalizeHost_StripsSchemeAndTrailingSlash()
     {