feat(dashboard): the daily-overview band becomes opt-in

The hero renders only when the layout carries the literal
heroVisible: true. Legacy blobs without the field, malformed values,
and fresh accounts all keep it off; the Settings toggle persists an
explicit opt-in through the existing layout PUT.

src/app/__tests__/dashboard-hero-wiring.test.ts

@@ -7,9 +7,9 @@ import { join } from "node:path";
  *
  * The hero band mounts between the page header and the tile strip:
  *
- *   - it gates on the layout's `heroVisible` flag (anything but the
- *     literal `false` renders — the resolver's clamp) AND on snapshot
- *     mode (the verdict needs the snapshot payload);
+ *   - it gates on the layout's `heroVisible` flag (only the literal
+ *     `true` renders — the hero is opt-in) AND on snapshot mode (the
+ *     verdict needs the snapshot payload);
  *   - while `primaryLoading` is true (same `!mounted ||` pin the tile
  *     silhouettes use) a footprint-identical skeleton holds the band,
  *     so the hero and the tiles swap to content in the SAME render
@@ -30,7 +30,7 @@ describe("dashboard hero — page wiring", () => {
 
   it("gates the hero on snapshot mode + the layout's heroVisible flag", () => {
     expect(src).toMatch(
-      /const\s+heroVisible\s*=\s*snapshotEnabled\s*&&\s*layout\.heroVisible\s*!==\s*false;/,
+      /const\s+heroVisible\s*=\s*snapshotEnabled\s*&&\s*layout\.heroVisible\s*===\s*true;/,
     );
   });
 

src/app/api/dashboard/widgets/__tests__/route.test.ts

@@ -477,7 +477,7 @@ describe("PUT /api/dashboard/widgets — heroVisible thread-through", () => {
     expect(updateArg.data.dashboardWidgetsJson.heroVisible).toBe(false);
   });
 
-  it("defaults heroVisible to true for a first save with no stored layout", async () => {
+  it("defaults heroVisible to false for a first save with no stored layout", async () => {
     vi.mocked(prisma.user.findUnique).mockResolvedValue({
       dashboardWidgetsJson: null,
     } as never);
@@ -495,7 +495,7 @@ describe("PUT /api/dashboard/widgets — heroVisible thread-through", () => {
       .calls[0]?.[0] as unknown as {
       data: { dashboardWidgetsJson: { heroVisible: boolean } };
     };
-    expect(updateArg.data.dashboardWidgetsJson.heroVisible).toBe(true);
+    expect(updateArg.data.dashboardWidgetsJson.heroVisible).toBe(false);
   });
 
   it("422s on a non-boolean heroVisible", async () => {

src/app/api/dashboard/widgets/route.ts

@@ -283,7 +283,7 @@ export const PUT = apiHandler(async (request: NextRequest) => {
       mergedChartOverlayPrefs = existingLayout.chartOverlayPrefs ?? {};
     }
     if (mergedHeroVisible === undefined) {
-      mergedHeroVisible = existingLayout.heroVisible !== false;
+      mergedHeroVisible = existingLayout.heroVisible === true;
     }
   }
   const normalized = serializeDashboardLayout({

src/app/page.tsx

@@ -709,13 +709,13 @@ export default function DashboardPage() {
   // hero band (it derives from the snapshot's server-computed
   // `greetingHour`, so the old client-side Intl hour walk retired
   // with it). The hero gates on the layout's `heroVisible` flag
-  // (default on; anything but the literal `false` renders) and holds
+  // (opt-in; only the literal `true` renders) and holds
   // a footprint-identical skeleton while the snapshot is in flight,
   // so the band swaps in place — no growth, no greeting flash. When
   // the hero does NOT render (toggle off, or snapshot flag off) the
   // header takes the greeting back — it must never disappear with the
   // band.
-  const heroVisible = snapshotEnabled && layout.heroVisible !== false;
+  const heroVisible = snapshotEnabled && layout.heroVisible === true;
   const heroSnapshot = snapshotQuery.data;
 
   return (