the development server gets av-club too

The cropper needs an encoder, and only the build was told where one is. That made development the one
place the old behaviour survived: the framing approved in the admin, the picture dev showed, and the
file that shipped would have been three different things — which is the class of bug this whole change
exists to remove.

The port is ephemeral by design, so it is read at start rather than written to a file. av-club moving
leaves dev pointing at a port that has gone; restarting dev from the panel fixes it, and startServer
already deletes and re-creates precisely so a changed port is picked up.

/images/ gets a year and immutable in the nginx config. Earned rather than assumed: the filename is a
hash of the original, the framing, the slot and the width, so the bytes at a URL cannot legitimately
change. That is the difference from /derived/, which is rewritten in place and therefore capped at
thirty days.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

api/static-site.ts

@@ -209,7 +209,11 @@ export async function buildSite(secrets: {
  * compression, and no cache headers at all, so every asset carried a TTL of zero and a returning
  * visitor re-downloaded the whole site.
  *
- * ── Three lifetimes, because there are three kinds of file ──
+ * ── Four lifetimes, because there are four kinds of file ──
+ *
+ * `images/` are placements cropped to their slot, named by a hash of everything that decides their
+ * bytes. A year, immutable, and earned: the file at that URL cannot change, because a change produces
+ * a different name. This is exactly what `derived/` cannot have.
  *
  * `derived/` renditions are rebuilt IN PLACE — av-club replaces the contents of `1280.webp` rather
  * than writing a new name. So they cannot be `immutable`, however much they look like they could be:
@@ -258,6 +262,15 @@ const NGINX_CONF = `server {
     add_header Cache-Control "public";
   }
 
+  # Placements cropped to their slot. A year and immutable, and this one is EARNED rather than assumed:
+  # the filename is a hash of the original, the framing, the slot and the width, so the bytes at a given
+  # URL can never legitimately change. A re-crop is a different name, and the HTML that carries it is
+  # revalidated every visit. This is the difference from /derived/ above, which is rewritten in place.
+  location ^~ /images/ {
+    expires 1y;
+    add_header Cache-Control "public, immutable";
+  }
+
   location ^~ /media/ {
     expires 30d;
     add_header Cache-Control "public";