feat(platform): detect distro, WSL, and architecture

internal/platform/platform_test.go

@@ -0,0 +1,45 @@
+package platform
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestParseDistroArch(t *testing.T) {
+	osRelease := `NAME="Arch Linux"
+ID=arch
+ID_LIKE=archlinux
+`
+	if got := parseDistro(strings.NewReader(osRelease)); got != DistroArch {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestParseDistroUbuntu(t *testing.T) {
+	osRelease := `NAME="Ubuntu"
+ID=ubuntu
+`
+	if got := parseDistro(strings.NewReader(osRelease)); got != DistroUnknown {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestParseDistroQuoted(t *testing.T) {
+	osRelease := `ID="arch"
+`
+	if got := parseDistro(strings.NewReader(osRelease)); got != DistroArch {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestDetectReturnsArch(t *testing.T) {
+	p, err := Detect()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Arch == "" {
+		t.Fatal("arch is empty")
+	}
+	// We don't assert Distro here because the test host may not be Arch.
+	// The parse-level tests above cover that logic.
+}