fix: fall back to portable RID for bundled CLI lookup on Linux (#424)

On Linux distros that install .NET from distribution packages (Ubuntu,
Fedora, RHEL, etc.), RuntimeInformation.RuntimeIdentifier returns
distro-specific RIDs like ubuntu.24.04-x64 instead of the portable
linux-x64. The bundled CLI is placed under runtimes/linux-x64/native/,
so the lookup fails and throws.

Fix both the runtime lookup and build-time RID resolution:

- Client.cs: GetBundledCliPath now falls back to the portable RID
  (e.g., linux-x64) when the distro-specific RID path doesn't exist.
- GitHub.Copilot.SDK.targets: Always use portable RIDs derived from
  OS/architecture detection instead of the project's RuntimeIdentifier,
  which may be distro-specific.

Fixes #424

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

Author: SteveSandersonMS

dotnet/src/Client.cs

@@ -999,7 +999,42 @@ private async Task VerifyProtocolVersionAsync(Connection connection, Cancellatio
         var binaryName = OperatingSystem.IsWindows() ? "copilot.exe" : "copilot";
         var rid = Path.GetFileName(System.Runtime.InteropServices.RuntimeInformation.RuntimeIdentifier);
         searchedPath = Path.Combine(AppContext.BaseDirectory, "runtimes", rid, "native", binaryName);
-        return File.Exists(searchedPath) ? searchedPath : null;
+        if (File.Exists(searchedPath))
+        {
+            return searchedPath;
+        }
+
+        // Fall back to portable RID (e.g., linux-x64) when distro-specific RID
+        // (e.g., ubuntu.24.04-x64) doesn't match the bundled path.
+        var portableRid = GetPortableRid();
+        if (portableRid != null && portableRid != rid)
+        {
+            var portablePath = Path.Combine(AppContext.BaseDirectory, "runtimes", portableRid, "native", binaryName);
+            if (File.Exists(portablePath))
+            {
+                return portablePath;
+            }
+        }
+
+        return null;
+    }
+
+    private static string? GetPortableRid()
+    {
+        string os;
+        if (OperatingSystem.IsWindows()) os = "win";
+        else if (OperatingSystem.IsLinux()) os = "linux";
+        else if (OperatingSystem.IsMacOS()) os = "osx";
+        else return null;
+
+        var arch = System.Runtime.InteropServices.RuntimeInformation.OSArchitecture switch
+        {
+            System.Runtime.InteropServices.Architecture.X64 => "x64",
+            System.Runtime.InteropServices.Architecture.Arm64 => "arm64",
+            _ => null,
+        };
+
+        return arch != null ? $"{os}-{arch}" : null;
     }
 
     private static (string FileName, IEnumerable<string> Args) ResolveCliCommand(string cliPath, IEnumerable<string> args)

dotnet/src/build/GitHub.Copilot.SDK.targets

@@ -3,9 +3,18 @@
   <!-- CopilotCliVersion is imported from GitHub.Copilot.SDK.props (generated at SDK build time, packaged alongside) -->
   <Import Project="$(MSBuildThisFileDirectory)GitHub.Copilot.SDK.props" Condition="'$(CopilotCliVersion)' == '' And Exists('$(MSBuildThisFileDirectory)GitHub.Copilot.SDK.props')" />
 
-  <!-- Resolve RID: use explicit RuntimeIdentifier, or infer from current machine -->
+  <!-- Resolve RID: use explicit RuntimeIdentifier (normalized to portable form) or infer from current machine.
+       Distro-specific RIDs like ubuntu.24.04-x64 are normalized to portable RIDs like linux-x64
+       so the bundled CLI path is consistent. -->
   <PropertyGroup>
-    <_CopilotRid Condition="'$(RuntimeIdentifier)' != ''">$(RuntimeIdentifier)</_CopilotRid>
+    <!-- Normalize explicit RuntimeIdentifier to portable RID if it's distro-specific -->
+    <_CopilotRid Condition="'$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.Contains('win')) And $(RuntimeIdentifier.EndsWith('-x64'))">win-x64</_CopilotRid>
+    <_CopilotRid Condition="'$(_CopilotRid)' == '' And '$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.Contains('win')) And $(RuntimeIdentifier.EndsWith('-arm64'))">win-arm64</_CopilotRid>
+    <_CopilotRid Condition="'$(_CopilotRid)' == '' And '$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.Contains('linux')) And $(RuntimeIdentifier.EndsWith('-x64'))">linux-x64</_CopilotRid>
+    <_CopilotRid Condition="'$(_CopilotRid)' == '' And '$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.Contains('linux')) And $(RuntimeIdentifier.EndsWith('-arm64'))">linux-arm64</_CopilotRid>
+    <_CopilotRid Condition="'$(_CopilotRid)' == '' And '$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.Contains('osx')) And $(RuntimeIdentifier.EndsWith('-x64'))">osx-x64</_CopilotRid>
+    <_CopilotRid Condition="'$(_CopilotRid)' == '' And '$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.Contains('osx')) And $(RuntimeIdentifier.EndsWith('-arm64'))">osx-arm64</_CopilotRid>
+    <!-- Fall back to machine detection when no RuntimeIdentifier is set -->
     <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('Windows')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'X64'">win-x64</_CopilotRid>
     <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('Windows')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'Arm64'">win-arm64</_CopilotRid>
     <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('Linux')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'X64'">linux-x64</_CopilotRid>