test: seed cached briefings with their generation moment

The today check now reads briefingGeneratedAt from the cached payload
and treats a payload without it as not from today. The integration
and e2e fixtures that seed a fresh briefing write it, as every real
generation does.

e2e/setup/ai-optional-fixture.ts

@@ -77,6 +77,8 @@ export async function resetAiOptionalAccount(): Promise<void> {
 export async function seedStoredBriefing(marker: string): Promise<void> {
   const insights = {
     dailyBriefing: { paragraph: marker, keyFindings: [] },
+    // Generated now: only text written today is served as today's read.
+    briefingGeneratedAt: new Date().toISOString(),
   };
   await withAccount(async (pool, userId) => {
     await pool.query(

tests/integration/ai-optional-mixed-routes.test.ts

@@ -93,7 +93,11 @@ async function seed(recordId: string): Promise<void> {
   await prisma.user.update({
     where: { id: recordId },
     data: {
-      insightsCachedText: JSON.stringify(BRIEFING),
+      // Generated now: only text written today is served as today's read.
+      insightsCachedText: JSON.stringify({
+        ...BRIEFING,
+        briefingGeneratedAt: new Date().toISOString(),
+      }),
       insightsCachedAt: new Date(),
       insightsCachedLocale: "en",
     },

tests/integration/briefing-cache-locale.test.ts

@@ -66,7 +66,11 @@ async function seedUserWithCachedBriefing(cachedLocale: string | null) {
       // snapshot read resolves the reader's locale from.
       locale: "de",
       insightsCachedAt: new Date(),
-      insightsCachedText: JSON.stringify({ dailyBriefing: BRIEFING }),
+      // Generated now: only text written today is served as today's read.
+      insightsCachedText: JSON.stringify({
+        dailyBriefing: BRIEFING,
+        briefingGeneratedAt: new Date().toISOString(),
+      }),
       insightsCachedLocale: cachedLocale,
       // The briefing is shown only while its AI capability is available, so
       // the account has its own provider (presence only) and a receipt.

tests/integration/sharing-front-door.test.ts

@@ -279,6 +279,8 @@ function cachedBriefing(marker: string): string {
       paragraph: `Briefing for the ${marker}. Second sentence.`,
       keyFindings: [],
     },
+    // Generated now: only text written today is served as today's read.
+    briefingGeneratedAt: new Date().toISOString(),
   });
 }