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, 1 insertions, 4 deletions

diff --git a/tests/e2e/resource_exhaustion_test.go b/tests/e2e/resource_exhaustion_test.go
index 3e60cdb..b5cdaf9 100644
--- a/tests/e2e/resource_exhaustion_test.go
+++ b/tests/e2e/resource_exhaustion_test.go
@@ -11,10 +11,7 @@ import (
 // TestResourceExhaustion ensures that repeatedly starting and stopping
 // tunnels does not leak mounts, file descriptors, or namespaces.
 func TestResourceExhaustion(t *testing.T) {
-	binaryPath, err := GetBinaryPath()
-	if err != nil {
-		t.Skipf("Skipping test: %v", err)
-	}
+	binaryPath := EnsureBinary(t)
 
 	tmpRuntimeDir := t.TempDir()
 	tmpConfigDir := t.TempDir()