refactor: unify tags and edges into single rels table

cmd/rel.go

@@ -3,14 +3,24 @@ package cmd
 import (
 	"axolotl/models"
 	"axolotl/service"
-	"fmt"
 	"strings"
 )
 
-// parseRelInput parses a "type:target" string into a RelInput.
+// parseRelInput parses a rel string into a RelInput.
+//
+// Formats:
+//   - "prefix::value"  → property rel with no target (tag)
+//   - "relname:target" → edge rel with a target node
+//   - "tagname"        → simple label rel with no target (alias for --tag)
 func parseRelInput(s string) (service.RelInput, error) {
-	if p := strings.SplitN(s, ":", 2); len(p) == 2 {
-		return service.RelInput{Type: models.RelType(p[0]), Target: p[1]}, nil
+	if strings.Contains(s, "::") {
+		// Property: name::value — no target node.
+		return service.RelInput{Type: models.RelType(s), Target: ""}, nil
 	}
-	return service.RelInput{}, fmt.Errorf("invalid relation format: %s (expected type:target)", s)
+	if idx := strings.Index(s, ":"); idx >= 0 {
+		// Edge rel: relname:target.
+		return service.RelInput{Type: models.RelType(s[:idx]), Target: s[idx+1:]}, nil
+	}
+	// Simple label tag — no target node.
+	return service.RelInput{Type: models.RelType(s), Target: ""}, nil
 }