新增: @use 同文件片段复用

支持 @use("name") 引用同一文件内 @tpl 定义的块，
消除 _list/_count 模板中 WHERE 条件重复问题。

internal/executor.go

@@ -15,6 +15,7 @@ type Executor struct {
 	style     PlaceholderStyle
 	rawPolicy rawValidator
 	strict    bool
+	blocks    map[string][]Node
 }
 
 type Result struct {
@@ -22,11 +23,12 @@ type Result struct {
 	Args []any
 }
 
-func NewExecutor(style PlaceholderStyle, rawPolicy rawValidator, strict bool) *Executor {
+func NewExecutor(style PlaceholderStyle, rawPolicy rawValidator, strict bool, blocks map[string][]Node) *Executor {
 	return &Executor{
 		style:     style,
 		rawPolicy: rawPolicy,
 		strict:    strict,
+		blocks:    blocks,
 	}
 }
 
@@ -99,6 +101,17 @@ func (e *Executor) walk(ctx *Context, ph *Placeholder, sql *strings.Builder, arg
 
 		case *BlockNode, *NamespaceNode, *IncludeNode, *CommentNode:
 			// skip
+		case *UseNode:
+			if e.blocks == nil {
+				return fmt.Errorf("line %d, col %d: @use(\"%s\") no blocks available", n.Pos.Line, n.Pos.Col, n.Name)
+			}
+			blockNodes, ok := e.blocks[n.Name]
+			if !ok {
+				return fmt.Errorf("line %d, col %d: @use(\"%s\") block not found", n.Pos.Line, n.Pos.Col, n.Name)
+			}
+			if err := e.walk(ctx, ph, sql, args, blockNodes); err != nil {
+				return err
+			}
 		}
 	}
 	return nil