feat: support primitive response arrays and shared catalog tooling

config/project.go

@@ -23,6 +23,9 @@ type EnvOptions struct {
 	Prefix string
 	Empty  string
 	Lookup func(string) (string, bool)
+	// Aliases maps canonical absolute environment names to ordered fallback names.
+	// A present canonical value wins, including an explicit empty value.
+	Aliases map[string][]string
 }
 
 // ApplyDefaults applies envDefault tags to zero fields before file overlays.
@@ -162,13 +165,22 @@ func projectOverlay[T any](base T, options EnvOptions, defaults bool) (T, error)
 			}
 			seen[key] = true
 			raw, present := options.Lookup(key)
+			selectedKey := key
+			if !present && !defaults {
+				for _, alias := range options.Aliases[key] {
+					if raw, present = options.Lookup(alias); present {
+						selectedKey = alias
+						break
+					}
+				}
+			}
 			if defaults {
 				raw, present = field.Tag.Lookup("envDefault")
 				present = present && dst.IsZero()
 			}
 			if present && raw == "" && !defaults {
 				if empty == "reject" {
-					return fmt.Errorf("config: %s must not be empty", key)
+					return fmt.Errorf("config: %s must not be empty", selectedKey)
 				}
 				if empty == "ignore" {
 					present = false
@@ -177,7 +189,7 @@ func projectOverlay[T any](base T, options EnvOptions, defaults bool) (T, error)
 			if present {
 				parsed := reflect.New(dst.Type()).Elem()
 				if err := parseEnvValue(parsed, raw); err != nil {
-					return fmt.Errorf("config: %s must be a valid %s", key, dst.Type())
+					return fmt.Errorf("config: %s must be a valid %s", selectedKey, dst.Type())
 				}
 				dst.Set(parsed)
 			}