perf: move 'use cache' to the data layer with cacheLife('max')

Per review feedback from @icyJoseph: instead of 'use cache' on every
page and generateMetadata, cache at the utility/data layer so callers
just work and the page render + generateMetadata share one compile.

- readMarkdownPage, collectSectionPaths, collectFlatSectionSlugs,
  loadErrorCodes, and a new compileErrorDecoderData helper are now
  'use cache' + cacheLife('max') (stable content, only changes on
  deploy; revalidate 30d instead of the default 15m).
- loadErrorDecoderData stays uncached and keeps the notFound() check,
  which can't run inside a 'use cache' scope; it delegates the cached
  compile to compileErrorDecoderData.
- Removed 'use cache' from all 9 routes and their generateMetadata.

Build unchanged: 816 routes, all Static / Partial Prerender.

Author: aurorascharff

src/app/blog/[[...slug]]/page.tsx

@@ -21,7 +21,6 @@ export async function generateStaticParams() {
 }
 
 export async function generateMetadata({params}: PageProps): Promise<Metadata> {
-  'use cache';
   const {slug} = await params;
   return sectionPageMetadata({
     section: 'blog',
@@ -31,7 +30,6 @@ export async function generateMetadata({params}: PageProps): Promise<Metadata> {
 }
 
 export default async function BlogPage({params}: PageProps) {
-  'use cache';
   const {slug} = await params;
   return renderSectionPage({
     section: 'blog',

src/app/community/[[...slug]]/page.tsx

@@ -21,7 +21,6 @@ export async function generateStaticParams() {
 }
 
 export async function generateMetadata({params}: PageProps): Promise<Metadata> {
-  'use cache';
   const {slug} = await params;
   return sectionPageMetadata({
     section: 'community',
@@ -30,7 +29,6 @@ export async function generateMetadata({params}: PageProps): Promise<Metadata> {
 }
 
 export default async function CommunityPage({params}: PageProps) {
-  'use cache';
   const {slug} = await params;
   return renderSectionPage({
     section: 'community',

src/app/errors/[errorCode]/page.tsx

@@ -19,13 +19,11 @@ export async function generateStaticParams() {
 }
 
 export async function generateMetadata({params}: PageProps): Promise<Metadata> {
-  'use cache';
   const {errorCode} = await params;
   return {title: `Minified React error #${errorCode}`};
 }
 
 export default async function ErrorDecoderPage({params}: PageProps) {
-  'use cache';
   const {errorCode} = await params;
   const data = await loadErrorDecoderData(errorCode);
   return <ErrorDecoderView data={data} pathname={`/errors/${errorCode}`} />;

src/app/errors/page.tsx

@@ -14,7 +14,6 @@ export const metadata: Metadata = {
 };
 
 export default async function ErrorDecoderIndex() {
-  'use cache';
   const data = await loadErrorDecoderData(null);
   return <ErrorDecoderView data={data} pathname="/errors" />;
 }

src/app/learn/[[...slug]]/page.tsx

@@ -21,7 +21,6 @@ export async function generateStaticParams() {
 }
 
 export async function generateMetadata({params}: PageProps): Promise<Metadata> {
-  'use cache';
   const {slug} = await params;
   return sectionPageMetadata({
     section: 'learn',
@@ -31,7 +30,6 @@ export async function generateMetadata({params}: PageProps): Promise<Metadata> {
 }
 
 export default async function LearnPage({params}: PageProps) {
-  'use cache';
   const {slug} = await params;
   return renderSectionPage({
     section: 'learn',

src/app/page.tsx

@@ -13,13 +13,11 @@ import {buildPageMetadata} from 'lib/buildPageMetadata';
 import {DocsPage} from './DocsPage';
 
 export async function generateMetadata(): Promise<Metadata> {
-  'use cache';
   const data = await readMarkdownPage([]);
   return buildPageMetadata({data, pathname: '/', section: 'home'});
 }
 
 export default async function HomePage() {
-  'use cache';
   const data = await readMarkdownPage([]);
   return (
     <DocsPage

src/app/reference/[[...slug]]/page.tsx

@@ -21,7 +21,6 @@ export async function generateStaticParams() {
 }
 
 export async function generateMetadata({params}: PageProps): Promise<Metadata> {
-  'use cache';
   const {slug} = await params;
   return sectionPageMetadata({
     section: 'reference',
@@ -30,7 +29,6 @@ export async function generateMetadata({params}: PageProps): Promise<Metadata> {
 }
 
 export default async function ReferencePage({params}: PageProps) {
-  'use cache';
   const {slug} = await params;
   return renderSectionPage({
     section: 'reference',

src/app/versions/page.tsx

@@ -11,12 +11,10 @@ import type {RouteItem} from 'components/Layout/getRouteMeta';
 import {renderSectionPage, sectionPageMetadata} from '../renderSectionPage';
 
 export async function generateMetadata(): Promise<Metadata> {
-  'use cache';
   return sectionPageMetadata({section: 'unknown', segments: ['versions']});
 }
 
 export default async function VersionsPage() {
-  'use cache';
   return renderSectionPage({
     section: 'unknown',
     segments: ['versions'],

src/app/warnings/[slug]/page.tsx

@@ -21,7 +21,6 @@ export async function generateStaticParams() {
 }
 
 export async function generateMetadata({params}: PageProps): Promise<Metadata> {
-  'use cache';
   const {slug} = await params;
   return sectionPageMetadata({
     section: 'unknown',
@@ -30,7 +29,6 @@ export async function generateMetadata({params}: PageProps): Promise<Metadata> {
 }
 
 export default async function WarningPage({params}: PageProps) {
-  'use cache';
   const {slug} = await params;
   return renderSectionPage({
     section: 'unknown',

src/lib/collectPaths.ts

@@ -9,6 +9,7 @@ import 'server-only';
 import fs from 'fs';
 import path from 'path';
 import {promisify} from 'util';
+import {cacheLife} from 'next/cache';
 
 const readdir = promisify(fs.readdir);
 const stat = promisify(fs.stat);
@@ -46,6 +47,8 @@ function getSegments(file: string): string[] {
 export async function collectSectionPaths(
   section: string
 ): Promise<string[][]> {
+  'use cache';
+  cacheLife('max');
   const dir = path.join(ROOT, section);
   if (!fs.existsSync(dir)) return [];
   const files = await getFiles(dir, dir);
@@ -64,6 +67,8 @@ export async function collectSectionPaths(
 export async function collectFlatSectionSlugs(
   section: string
 ): Promise<string[]> {
+  'use cache';
+  cacheLife('max');
   const dir = path.join(ROOT, section);
   if (!fs.existsSync(dir)) return [];
   const entries = await readdir(dir);