feat(export-options): Google Sheets 템플릿 모드 옵션(UI+extras) 추가

lib/exporter/extras.ts

@@ -9,6 +9,7 @@ export type ExtrasOverrides = {
     display: string
     theme_color: string
   }>
+  sheetsMode?: 'auto' | 'include' | 'exclude'
 }
 
 function toBytes(s: string): Uint8Array {
@@ -42,10 +43,12 @@ export function buildExtrasForPage(page: Page, overrides?: ExtrasOverrides): Rec
   const manifestJson = JSON.stringify(manifestMerged, null, 2)
   out['site.webmanifest'] = toBytes(manifestJson)
 
-  // Google Sheets 템플릿: actionUrl 미지정 시 포함
+  // Google Sheets 템플릿: 기본 auto. overrides.sheetsMode로 강제 포함/제외 가능
+  const mode = overrides?.sheetsMode ?? 'auto'
   const action = page.form?.actionUrl?.trim()
   const hasAction = !!(action && action.length > 0)
-  if (!hasAction) {
+  const shouldInclude = mode === 'include' || (mode === 'auto' && !hasAction)
+  if (shouldInclude) {
     const code = `/**
  * Google Apps Script Web App for form submissions
  * - Deploy as Web App and set URL as form action if needed.