Deploy main eacf1e7 to prod

Replaces #559, which conflicted.

Model: opus-5-5

script/fmt

@@ -1,5 +1,8 @@
 #!/bin/sh
-# script/fmt: format all files (writes).
+# script/fmt: format all files (writes): the Go code with gofmt and
+# goimports, the Markdown with prettier. prettier is never installed
+# locally: it runs in docker, in the Dockerfile's Markdown stages, built
+# with --no-cache like every docker build in script/.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
@@ -10,6 +13,8 @@ main() {
     if command -v goimports >/dev/null 2>&1; then
         goimports -w .
     fi
+    docker build --no-cache \
+        --target markdown-output --output type=local,dest=. .
 }
 
 main "$@"