feat(cli): wire arch-binary subcommand

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <[email protected]>

cmd/zeta-reconstruct/main_test.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestNormalizeArgs(t *testing.T) {
+	valueFlags := map[string]bool{
+		"--output": true,
+		"--repo":   true,
+		"--arch":   true,
+	}
+
+	tests := []struct {
+		name string
+		in   []string
+		want []string
+	}{
+		{
+			name: "flags after positional",
+			in:   []string{"input.pkg.tar.zst", "--output", "/tmp/out"},
+			want: []string{"--output", "/tmp/out", "input.pkg.tar.zst"},
+		},
+		{
+			name: "flags before positional",
+			in:   []string{"--output", "/tmp/out", "input.pkg.tar.zst"},
+			want: []string{"--output", "/tmp/out", "input.pkg.tar.zst"},
+		},
+		{
+			name: "flag=value form",
+			in:   []string{"input.pkg.tar.zst", "--output=/tmp/out"},
+			want: []string{"--output=/tmp/out", "input.pkg.tar.zst"},
+		},
+		{
+			name: "unknown flag stays a flag",
+			in:   []string{"input.pkg.tar.zst", "--bogus"},
+			want: []string{"--bogus", "input.pkg.tar.zst"},
+		},
+		{
+			name: "value-taking flag at end without value",
+			in:   []string{"input.pkg.tar.zst", "--output"},
+			want: []string{"--output", "input.pkg.tar.zst"},
+		},
+		{
+			name: "mixed flags and positionals keep order",
+			in:   []string{"--repo", "https://x", "a.zst", "--output", "/tmp/out", "b.zst"},
+			want: []string{"--repo", "https://x", "--output", "/tmp/out", "a.zst", "b.zst"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := normalizeArgs(tt.in, valueFlags)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Fatalf("normalizeArgs(%v) = %v, want %v", tt.in, got, tt.want)
+			}
+		})
+	}
+}