Refactor : improve TestDeleteContext robustness and isolation using temporary directories

Reason/Context

Currently, TestDeleteContext in cmd/context_test.go relies on a hardcoded file path
/testdata/local.config

This approach causes the test to fail on filesystems that do not fully
support Unix-style permissions (such as NTFS or FAT32 partitions commonly used on external drives or
Windows-mounted volumes), as the test attempts to verify restrictive file permissions (0600).

Description

The enhancement involves refactoring the TestDeleteContext function. Instead of using a static file
path, the test will now:

1. Utilize t.TempDir() to create a unique, isolated directory for each test run.
2. Construct the configuration file path dynamically using filepath.Join()
3. Clean up automatically after the test finishes, as t.TempDir() is managed by the Go testing
   package.

Implementation ideas

No response

Abre cmd/context_test.go y empieza con TestDeleteContext. Ejecuta esa prueba para observar su comportamiento actual y, después, verifica que la prueba use t.TempDir() y filepath.Join() en lugar de la ruta codificada de forma fija. La tarea estará terminada cuando la prueba siga estando aislada, realice la limpieza automáticamente y pase en los sistemas de archivos compatibles.