chore(www): add /evals to the sitemap (#49226)

<!-- ccr-slack-attribution -->
_Requested by **Sean Oliver** · [Slack
thread](https://supabase.slack.com/archives/C07P3AU3J2D/p1787036390117589?thread_ts=1787036390.117589&cid=C07P3AU3J2D)_

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

YES

## What kind of change does this PR introduce?

Chore. One entry added to the www sitemap generator.

## What is the current behavior?

`https://supabase.com/evals` is missing from `sitemap_www.xml`, so
search crawlers are never told the page exists. `robots.txt` doesn't
block it, they just have no way to find it from the sitemap.

The reason is that `/evals` is served by a separate Vercel project and
only reaches supabase.com through a proxy rewrite in
`apps/www/lib/rewrites.js`:

```js
{
  source: '/evals',
  destination: 'https://supabase-evals.vercel.app',
},
```

`apps/www/internals/generate-sitemap.mjs` builds its URL list by
globbing local route source files (`pages/**`, `_blog/*.mdx`,
prerendered `.next/server/pages/**`, etc.) and never resolves rewrites.
There is no page file behind `/evals`, so the globs can't discover it.

Closes GROWTH-1113.

## What is the new behavior?

`https://supabase.com/evals` appears once in the generated
`sitemap_www.xml`, with the same `<changefreq>weekly</changefreq>` and
`<priority>0.5</priority>` as every other entry in the file (no entry in
this sitemap carries a `<lastmod>`).

The entry is a small named const spread into the final `urlset` join,
next to `changelogDetailUrls` — the existing precedent in this file for
URLs with no page file behind them. Nothing else in the script changed,
and the sitemap index output (`sitemap.xml`) is byte-identical.

```diff
+  // /evals is a separate app proxied onto supabase.com via a rewrite in lib/rewrites.js,
+  // so it has no page file for the globs above to find. Hardcode it here.
+  const proxiedAppUrls = [
+    `
+        <url>
+            <loc>https://supabase.com/evals</loc>
+            <changefreq>weekly</changefreq>
+            <priority>0.5</priority>
+        </url>
+      `,
+  ]
+
   const sitemap = `
     <?xml version="1.0" encoding="UTF-8"?>
     <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
-        ${[...staticUrls, ...changelogDetailUrls].join('')}
+        ${[...staticUrls, ...changelogDetailUrls, ...proxiedAppUrls].join('')}
     </urlset>
     `
```

This only makes the URL discoverable. Whether the page content itself is
crawlable is separate work, tracked in the evals repo.

## Additional context

Verification, run locally against this branch. The generator runs
standalone (`node ./internals/generate-sitemap.mjs` from `apps/www`); a
missing `.next` just means the globs match fewer pages, and the missing
changelog RSS is caught internally.

I generated `sitemap_www.xml` from `master` and from this branch and
diffed the two. The added entry is the only difference:

```
3271a3272,3277
>
>   <url>
>     <loc>https://supabase.com/evals</loc>
>     <changefreq>weekly</changefreq>
>     <priority>0.5</priority>
>   </url>
```

Exactly one occurrence, with its neighbouring entry for context:

```
$ grep -c '<loc>https://supabase.com/evals</loc>' public/sitemap_www.xml
1

  <url>
    <loc>https://supabase.com/terms</loc>
    <changefreq>weekly</changefreq>
    <priority>0.5</priority>
  </url>

  <url>
    <loc>https://supabase.com/evals</loc>
    <changefreq>weekly</changefreq>
    <priority>0.5</priority>
  </url>
</urlset>
```

Other checks:

- Both outputs parse as well-formed XML (Python `xml.dom.minidom`):
`sitemap_www.xml` has 545 `<url>` elements, `sitemap.xml` parses OK.
- `sitemap.xml` (the sitemap index) is identical to the pre-change
output; `diff` reports no changes.
- `npx prettier --check internals/generate-sitemap.mjs` → "All matched
files use Prettier code style!"
- Both generated sitemaps are gitignored (`apps/www/.gitignore` lines
29-30), confirmed with `git check-ignore`. `git status` shows only
`apps/www/internals/generate-sitemap.mjs`, so no generated file is in
the commit.
- No test, snapshot, or fixture anywhere in the repo references the
sitemap generator, so there was nothing to run. Its only caller is
`apps/www`'s `postbuild` script.

Not run: `pnpm --filter=www build`. It fails during "Collecting page
data" on a clean `master` checkout in this environment too, so the
failure is pre-existing and unrelated, and this change needs no build to
verify.

Co-authored-by: Claude <noreply@anthropic.com>

apps/www/internals/generate-sitemap.mjs

@@ -139,10 +139,22 @@ async function generate() {
     }
   })()
 
+  // /evals is a separate app proxied onto supabase.com via a rewrite in lib/rewrites.js,
+  // so it has no page file for the globs above to find. Hardcode it here.
+  const proxiedAppUrls = [
+    `
+        <url>
+            <loc>https://supabase.com/evals</loc>
+            <changefreq>weekly</changefreq>
+            <priority>0.5</priority>
+        </url>
+      `,
+  ]
+
   const sitemap = `
     <?xml version="1.0" encoding="UTF-8"?>
     <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
-        ${[...staticUrls, ...changelogDetailUrls].join('')}
+        ${[...staticUrls, ...changelogDetailUrls, ...proxiedAppUrls].join('')}
     </urlset>
     `