fix(auth): strip model suffix in GitHub Copilot executor before upstream call

GitHub Copilot API rejects model names with suffixes (e.g. claude-opus-4.6(medium)).
The OAuthModelAlias resolution correctly maps aliases like 'opus(medium)' to
'claude-opus-4.6(medium)' preserving the suffix, but the executor must strip the
suffix before sending to the upstream API since Copilot only accepts bare model names.

Update normalizeModel in github_copilot_executor to strip suffixes using
thinking.ParseSuffix, matching the pattern used by other executors.

Also add test coverage for:
- OAuthModelAliasChannel github-copilot and kiro channel resolution
- Suffix preservation in alias resolution for github-copilot
- normalizeModel suffix stripping in github_copilot_executor

internal/runtime/executor/github_copilot_executor.go

@@ -14,6 +14,7 @@ import (
 	"github.com/google/uuid"
 	copilotauth "github.com/router-for-me/CLIProxyAPI/v6/internal/auth/copilot"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/thinking"
 	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
 	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/executor"
 	sdktranslator "github.com/router-for-me/CLIProxyAPI/v6/sdk/translator"
@@ -471,9 +472,14 @@ func detectVisionContent(body []byte) bool {
 	return false
 }
 
-// normalizeModel is a no-op as GitHub Copilot accepts model names directly.
-// Model mapping should be done at the registry level if needed.
-func (e *GitHubCopilotExecutor) normalizeModel(_ string, body []byte) []byte {
+// normalizeModel strips the suffix (e.g. "(medium)") from the model name
+// before sending to GitHub Copilot, as the upstream API does not accept
+// suffixed model identifiers.
+func (e *GitHubCopilotExecutor) normalizeModel(model string, body []byte) []byte {
+	baseModel := thinking.ParseSuffix(model).ModelName
+	if baseModel != model {
+		body, _ = sjson.SetBytes(body, "model", baseModel)
+	}
 	return body
 }
 

internal/runtime/executor/github_copilot_executor_test.go

@@ -0,0 +1,54 @@
+package executor
+
+import (
+	"testing"
+
+	"github.com/tidwall/gjson"
+)
+
+func TestGitHubCopilotNormalizeModel_StripsSuffix(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name      string
+		model     string
+		wantModel string
+	}{
+		{
+			name:      "suffix stripped",
+			model:     "claude-opus-4.6(medium)",
+			wantModel: "claude-opus-4.6",
+		},
+		{
+			name:      "no suffix unchanged",
+			model:     "claude-opus-4.6",
+			wantModel: "claude-opus-4.6",
+		},
+		{
+			name:      "different suffix stripped",
+			model:     "gpt-4o(high)",
+			wantModel: "gpt-4o",
+		},
+		{
+			name:      "numeric suffix stripped",
+			model:     "gemini-2.5-pro(8192)",
+			wantModel: "gemini-2.5-pro",
+		},
+	}
+
+	e := &GitHubCopilotExecutor{}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			body := []byte(`{"model":"` + tt.model + `","messages":[]}`)
+			got := e.normalizeModel(tt.model, body)
+
+			gotModel := gjson.GetBytes(got, "model").String()
+			if gotModel != tt.wantModel {
+				t.Fatalf("normalizeModel() model = %q, want %q", gotModel, tt.wantModel)
+			}
+		})
+	}
+}