fix(oauth): request repository deletion scope

Include delete_repo in the supported OAuth scope set used by stdio login, HTTP protected-resource metadata, and tool filtering.

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

Copilot-Session: 4b04480c-c2e9-483e-9b0f-34830b76a2f8

Author: SamMorrowDrums

pkg/http/oauth/oauth.go

@@ -28,6 +28,7 @@ const (
 // requirements when scopes change.
 var SupportedScopes = []string{
 	"repo",
+	"delete_repo",
 	"read:org",
 	"read:user",
 	"user:email",

pkg/http/oauth/oauth_test.go

@@ -569,6 +569,7 @@ func TestSupportedScopes(t *testing.T) {
 	// Verify all expected scopes are present
 	expectedScopes := []string{
 		"repo",
+		"delete_repo",
 		"read:org",
 		"read:user",
 		"user:email",