feat: load explicit configuration references and remove implicit env overlays

cmd/go-omni/apigen/upgrade.go

@@ -14,7 +14,9 @@ import (
 	"golang.org/x/mod/semver"
 	"os"
 	"path/filepath"
+	"reflect"
 	"sort"
+	"strconv"
 	"strings"
 )
 
@@ -54,6 +56,22 @@ func checkConfigLoadExtension(root string) error {
 		if err != nil {
 			return fmt.Errorf("parse %s: %w", rel, err)
 		}
+		var removed bool
+		ast.Inspect(f, func(n ast.Node) bool {
+			field, ok := n.(*ast.Field)
+			if ok && field.Tag != nil {
+				if raw, e := strconv.Unquote(field.Tag.Value); e == nil {
+					tag := reflect.StructTag(raw)
+					_, a := tag.Lookup("env")
+					_, b := tag.Lookup("envDefault")
+					removed = removed || a || b
+				}
+			}
+			return true
+		})
+		if removed {
+			return fmt.Errorf("%s: env/envDefault tags were removed; migrate defaults and explicit file references before generating; see CONFIG.md", rel)
+		}
 		for _, decl := range f.Decls {
 			if fn, ok := decl.(*ast.FuncDecl); ok && fn.Recv == nil && fn.Name.Name == "Load" {
 				return fmt.Errorf("%s: migrate the project-owned Load function before generating internal/config/loadGen.go; retain Config/Default/Validate and move decoder options to NewLoader; see CONFIG.md", rel)