feat: podman-compose stack units and root/user execution scopes

- syncup: podman first, docker only as fallback (podman wins on name clash;
  existing docker units found in podman switch to podman)
- syncup: group podman-compose containers into one `kind: stack` unit per
  project (project, working_dir, compose_files, compose_bin from labels);
  disable existing member units ("part of stack <project>")
- generator: compose mode (podman-compose up/stop, WorkingDirectory) with
  pod start/stop fallback when compose binary/dir/files are missing
- reconcile: stacks disabled with "stack not found" when neither compose
  files nor pod exist
- root: scan root + rootless users listed in `users:` (podman only)
- non-root: config ~/.config/unitdore/units.yaml, own user units only
- sysuser package: runuser with XDG_RUNTIME_DIR/DBUS env, home/linger lookup
- install: warn when linger is not enabled for user units
- testdata/stack: podman-compose test stack and captured podman ps fixture
- docs: README, generated-units, man page, AGENTS, PLAN

systemd/generator_test.go

@@ -1,6 +1,8 @@
 package systemd
 
 import (
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -263,3 +265,129 @@ func TestBuildExecCommands(t *testing.T) {
 		})
 	}
 }
+
+// newComposeStack creates a stack unit whose compose binary, working dir and
+// compose file exist on disk (compose mode).
+func newComposeStack(t *testing.T) config.Unit {
+	t.Helper()
+	dir := t.TempDir()
+	bin := filepath.Join(dir, "podman-compose")
+	if err := os.WriteFile(bin, []byte("#!/bin/sh\n"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "compose.yaml"), []byte("services: {}\n"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	return config.Unit{
+		Name:         "shop",
+		Runtime:      "podman",
+		Kind:         config.KindStack,
+		Project:      "shop",
+		WorkingDir:   dir,
+		ComposeFiles: []string{"compose.yaml"},
+		ComposeBin:   bin,
+		Enabled:      true,
+	}
+}
+
+func TestStackMode(t *testing.T) {
+	u := newComposeStack(t)
+	if StackMode(u) != StackModeCompose {
+		t.Errorf("StackMode() = %q, want compose", StackMode(u))
+	}
+
+	missingFile := u
+	missingFile.ComposeFiles = []string{"gone.yaml"}
+	if StackMode(missingFile) != StackModePod {
+		t.Error("missing compose file should fall back to pod mode")
+	}
+
+	missingBin := u
+	missingBin.ComposeBin = ""
+	if StackMode(missingBin) != StackModePod {
+		t.Error("missing compose binary should fall back to pod mode")
+	}
+
+	missingDir := u
+	missingDir.WorkingDir = "/nonexistent/unitdore-test"
+	if StackMode(missingDir) != StackModePod {
+		t.Error("missing working dir should fall back to pod mode")
+	}
+}
+
+func TestGenerate_StackCompose(t *testing.T) {
+	u := newComposeStack(t)
+	content, err := Generate(u, "", "")
+	if err != nil {
+		t.Fatalf("Generate() error: %v", err)
+	}
+	base := u.ComposeBin + " -p shop -f compose.yaml"
+	for _, want := range []string{
+		"Description=Unitdore: shop (podman-compose stack)",
+		"Type=simple",
+		"WorkingDirectory=" + u.WorkingDir,
+		"ExecStart=" + base + " up",
+		"ExecStop=-" + base + " stop",
+		"WantedBy=multi-user.target",
+	} {
+		if !strings.Contains(content, want) {
+			t.Errorf("Generate() missing %q in output:\n%s", want, content)
+		}
+	}
+	if strings.Contains(content, "RemainAfterExit") || strings.Contains(content, "Requires=") {
+		t.Errorf("compose stack unit has unexpected directives:\n%s", content)
+	}
+}
+
+func TestGenerate_StackPodFallback(t *testing.T) {
+	u := newComposeStack(t)
+	u.ComposeBin = ""
+	u.User = "hein"
+	content, err := Generate(u, "", "")
+	if err != nil {
+		t.Fatalf("Generate() error: %v", err)
+	}
+	for _, want := range []string{
+		"Description=Unitdore: shop (podman pod)",
+		"Type=oneshot",
+		"RemainAfterExit=yes",
+		"ExecStart=/usr/bin/podman pod start pod_shop",
+		"ExecStop=-/usr/bin/podman pod stop pod_shop",
+		"WantedBy=default.target",
+	} {
+		if !strings.Contains(content, want) {
+			t.Errorf("Generate() missing %q in output:\n%s", want, content)
+		}
+	}
+	if strings.Contains(content, "WorkingDirectory=") {
+		t.Errorf("pod fallback should not set WorkingDirectory:\n%s", content)
+	}
+}
+
+func TestGenerate_StackCustomCommand(t *testing.T) {
+	u := newComposeStack(t)
+	u.Command = "/usr/local/bin/stack.sh"
+	content, err := Generate(u, "", "")
+	if err != nil {
+		t.Fatalf("Generate() error: %v", err)
+	}
+	if !strings.Contains(content, "ExecStart=/usr/local/bin/stack.sh") {
+		t.Errorf("custom command should override stack commands:\n%s", content)
+	}
+}
+
+func TestBuildComposeCommands_Quoting(t *testing.T) {
+	u := config.Unit{
+		Project:      "shop",
+		ComposeBin:   "/usr/bin/podman-compose",
+		ComposeFiles: []string{"compose.yaml", "my override.yaml"},
+	}
+	start, stop := buildComposeCommands(u)
+	wantBase := `/usr/bin/podman-compose -p shop -f compose.yaml -f "my override.yaml"`
+	if start != wantBase+" up" {
+		t.Errorf("start = %q", start)
+	}
+	if stop != wantBase+" stop" {
+		t.Errorf("stop = %q", stop)
+	}
+}