perf: migrate pages to Cache Components via root layout opt-out

Remove the per-route 'export const instant = false' opt-outs now that the root layout carries the single Cache Components opt-out. Child pages inherit the opt-out, so admin/mod/radio leaf pages that only access cached or DB data stay instant while runtime-dependent pages remain dynamic. Update the staff-smoke contract test to assert the root-layout contract.

src/lib/staff-smoke-contract.test.ts

@@ -112,12 +112,18 @@ describe("staff smoke contract", () => {
 		walk("src/app/mod");
 		expect(legacyHits).toBe(0);
 
-		// Both staff layouts opt out of Cache Components (was force-dynamic).
-		expect(readFileSync("src/app/admin/layout.tsx", "utf8")).toContain(
+		// The root layout carries the single Cache Components opt-out; staff
+		// pages inherit it (was force-dynamic, then per-layout instant=false).
+		expect(readFileSync("src/app/layout.tsx", "utf8")).toContain(
 			"export const instant = false",
 		);
-		expect(readFileSync("src/app/mod/layout.tsx", "utf8")).toContain(
-			"export const instant = false",
+		// Staff layouts must not redeclare the opt-out — that is the root
+		// layout's job now, and redeclaring it is the legacy per-layout pattern.
+		expect(readFileSync("src/app/admin/layout.tsx", "utf8")).not.toContain(
+			"export const instant",
+		);
+		expect(readFileSync("src/app/mod/layout.tsx", "utf8")).not.toContain(
+			"export const instant",
 		);
 	});