docs: add production plan management screen implementation guide

- Introduced a comprehensive implementation guide for the production plan management screen, detailing the overall structure, table mappings, and V2 component capabilities.
- Included specific information on the main tables used, their columns, and how they relate to the screen's functionality.
- Provided an analysis of existing V2 components that can be utilized, along with those that require further development or customization.
- This guide aims to facilitate the development process and ensure adherence to established standards for screen implementation.

Made-with: Cursor

frontend/lib/registry/components/v2-split-panel-layout/SplitPanelLayoutComponent.tsx

@@ -4384,9 +4384,8 @@ export const SplitPanelLayoutComponent: React.FC<SplitPanelLayoutComponentProps>
                 }
               })()
             ) : componentConfig.rightPanel?.displayMode === "custom" ? (
-              // 🆕 커스텀 모드: 패널 안에 자유롭게 컴포넌트 배치
-              // 실행 모드에서 좌측 미선택 시 안내 메시지 표시
-              !isDesignMode && !selectedLeftItem ? (
+              // 커스텀 모드: alwaysShow가 아닌 경우에만 좌측 선택 필요
+              !isDesignMode && !selectedLeftItem && !componentConfig.rightPanel?.alwaysShow ? (
                 <div className="flex h-full items-center justify-center">
                   <div className="text-muted-foreground text-center text-sm">
                     <p className="mb-2">좌측에서 항목을 선택하세요</p>