seo(landing): serve the IndexNow key file

apps/landing/src/__tests__/indexnow.test.ts

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+import { existsSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { describe, expect, it } from 'vitest'
+import { INDEXNOW_KEY, INDEXNOW_KEY_PATH } from '@/lib/indexnow'
+import { GET } from '../app/5cb30cbda540958e8d033652400e59e3.txt/route'
+
+// IndexNow verification hinges on one brittle coupling: the App Router
+// directory that serves the key file is NAMED after the key, so a change to
+// the constant without the matching directory rename (or vice versa) leaves
+// the site serving one key while claiming another — and every submission an
+// engine receives fails ownership. These pin the two to each other, plus the
+// response shape indexnow.org requires (exact body, text/plain).
+describe('IndexNow key file served by the landing app', () => {
+    it('key constant is 32 lowercase hexadecimal characters as IndexNow requires', () => {
+        expect(INDEXNOW_KEY).toMatch(/^[0-9a-f]{32}$/)
+    })
+
+    it('key path constant is the key served as a root-level .txt file', () => {
+        expect(INDEXNOW_KEY_PATH).toBe(`/${INDEXNOW_KEY}.txt`)
+    })
+
+    it('route directory on disk is named exactly after the key constant', () => {
+        const appDir = fileURLToPath(new URL('../app/', import.meta.url))
+        expect(existsSync(`${appDir}${INDEXNOW_KEY}.txt/route.ts`)).toBe(true)
+    })
+
+    it('GET responds with the bare key as plain text and nothing else', async () => {
+        const response = GET()
+
+        expect(response.status).toBe(200)
+        expect(response.headers.get('content-type')).toBe(
+            'text/plain; charset=utf-8',
+        )
+        await expect(response.text()).resolves.toBe(INDEXNOW_KEY)
+    })
+})

apps/landing/src/app/5cb30cbda540958e8d033652400e59e3.txt/route.ts

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+import { INDEXNOW_KEY } from '@/lib/indexnow'
+
+// The IndexNow ownership key file. The directory name above is the key and
+// must match INDEXNOW_KEY exactly — src/__tests__/indexnow.test.ts pins it.
+// Static: the body is a constant, so there is nothing to compute per request.
+export const dynamic = 'force-static'
+
+export function GET() {
+    return new Response(INDEXNOW_KEY, {
+        headers: {
+            'Content-Type': 'text/plain; charset=utf-8',
+            'Cache-Control': 'public, max-age=86400',
+        },
+    })
+}

apps/landing/src/lib/indexnow.ts

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+// IndexNow (https://www.indexnow.org/documentation) lets a site push URL
+// changes to participating engines (Bing, Yandex, Seznam, Naver) instead of
+// waiting to be recrawled. Ownership is proved by hosting a key file: a plain
+// text file at `https://<host>/<key>.txt` whose body is EXACTLY the key, served
+// as `text/plain`. An engine fetches it when a submission arrives; a missing,
+// redirected, or differently-bodied file makes every submission fail.
+//
+// This module is the single source of truth for that key. The route directory
+// `src/app/<key>.txt/` must stay byte-identical to INDEXNOW_KEY — a rename in
+// one place and not the other silently breaks verification, so
+// `src/__tests__/indexnow.test.ts` pins the two together.
+//
+// Submissions are NOT made from this app. Serving the key is the prerequisite;
+// pushing URLs is an operational step run separately, after this deploys.
+export const INDEXNOW_KEY = '5cb30cbda540958e8d033652400e59e3'
+
+export const INDEXNOW_KEY_PATH = `/${INDEXNOW_KEY}.txt`