fix: avoid infinite loops when searching for filesystem root of another drive (#353)

Co-authored-by: Claude <svc-devxp-claude@slack-corp.com>

Author: zimeg

internal/shared/clients.go

@@ -222,7 +222,12 @@ func (c *ClientFactory) InitSDKConfig(ctx context.Context, dirPath string) error
 			return slackerror.New(slackerror.ErrHooksJSONLocation)
 		}
 		// Move upward one directory level
-		dirPath = filepath.Dir(dirPath)
+		parentDir := filepath.Dir(dirPath)
+		if parentDir == dirPath {
+			// Reached a filesystem root not covered above (e.g. D:\ when SYSTEMROOT is on C:\)
+			return slackerror.New(slackerror.ErrHooksJSONLocation)
+		}
+		dirPath = parentDir
 	}
 	configFileBytes, err := afero.ReadFile(c.Fs, hooksJSONFilePath)
 	if err != nil {

internal/shared/clients_test.go

@@ -110,6 +110,12 @@ func Test_ClientFactory_InitSDKConfig(t *testing.T) {
 			mockWorkingDirectory:  filepath.Join("path", "outside", "home", "to", "project"),
 			expectedError:         slackerror.New(slackerror.ErrHooksJSONLocation),
 		},
+		"errors if traversal reaches a filesystem root": {
+			mockHooksJSONContent:  "{}",
+			mockHooksJSONFilePath: filepath.Join(string(filepath.Separator), "other", "volume", "project", "package.json"),
+			mockWorkingDirectory:  filepath.Join(string(filepath.Separator), "other", "volume", "project"),
+			expectedError:         slackerror.New(slackerror.ErrHooksJSONLocation),
+		},
 	}
 	for name, tc := range tests {
 		t.Run(name, func(t *testing.T) {