Initial commit: unitdore scaffold + syncup/edit commands

- config: load/save/add unit, Unit struct
- runtime: podman + docker discovery and exists check
- cmd: syncup (discover + reconcile), edit, cobra root
- PLAN.md: full project plan

runtime/podman.go

@@ -0,0 +1,73 @@
+package runtime
+
+import (
+	"encoding/json"
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+type Podman struct{}
+
+func (p *Podman) Name() string { return "podman" }
+
+type podmanContainer struct {
+	Names   []string `json:"Names"`
+	Image   string   `json:"Image"`
+	Command string   `json:"Command"`
+	State   string   `json:"State"`
+}
+
+func (p *Podman) ListRunning() ([]Container, error) {
+	bin, err := exec.LookPath("podman")
+	if err != nil {
+		return nil, nil // podman not installed — not an error
+	}
+
+	out, err := exec.Command(bin, "ps", "--format", "json").Output()
+	if err != nil {
+		return nil, fmt.Errorf("podman ps: %w", err)
+	}
+
+	var raw []podmanContainer
+	if err := json.Unmarshal(out, &raw); err != nil {
+		return nil, fmt.Errorf("parsing podman output: %w", err)
+	}
+
+	var containers []Container
+	for _, c := range raw {
+		name := ""
+		if len(c.Names) > 0 {
+			name = c.Names[0]
+		}
+		if name == "" {
+			continue
+		}
+		containers = append(containers, Container{
+			Name:    name,
+			Image:   c.Image,
+			Command: c.Command,
+			Runtime: "podman",
+		})
+	}
+	return containers, nil
+}
+
+func (p *Podman) Exists(name string) (bool, error) {
+	bin, err := exec.LookPath("podman")
+	if err != nil {
+		return false, nil
+	}
+
+	out, err := exec.Command(bin, "ps", "-a", "--format", "{{.Names}}").Output()
+	if err != nil {
+		return false, fmt.Errorf("podman ps -a: %w", err)
+	}
+
+	for _, line := range strings.Split(string(out), "\n") {
+		if strings.TrimSpace(line) == name {
+			return true, nil
+		}
+	}
+	return false, nil
+}