refactor: decouple namespace operations and improve test coverage

- Introduce `namespace.Ops` interface to decouple `Manager` from system-level namespace operations, enabling easier unit testing via mocks.
- Add unit tests for `internal/paths` to verify path resolution logic across different environment configurations.
- Implement `EnsureBinary` helper in E2E tests to gracefully skip tests when `WG_WRAP_BIN` is not set, allowing `go test ./...` to pass in non-build environments.
- Apply project-wide formatting and fix linting issues.

1 files changed, 11 insertions, 0 deletions

diff --git a/tests/e2e/test_helpers.go b/tests/e2e/test_helpers.go
index 6d65011..93e851c 100644
--- a/tests/e2e/test_helpers.go
+++ b/tests/e2e/test_helpers.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"strings"
+	"testing"
 )
 
 // GetBinaryPath resolves the path to the wg-wrap binary.
@@ -21,6 +22,16 @@ func GetBinaryPath() (string, error) {
 	return path, nil
 }
 
+// EnsureBinary returns the path to the wg-wrap binary or skips the test if it's not available.
+func EnsureBinary(t *testing.T) string {
+	t.Helper()
+	bin, err := GetBinaryPath()
+	if err != nil {
+		t.Skipf("skipping test: %v", err)
+	}
+	return bin
+}
+
 // SetEnvOverrides returns a new slice of environment variables with the provided overrides applied.
 // It ensures that overriding an existing variable replaces it rather than appending it.
 func SetEnvOverrides(overrides map[string]string) []string {