Model the build on mozimo and target emily

- Makefile: PLATFORMS, tags :<commit> and :main, build-check with --pull.
- deploy.sh: push, guards, git pull --ff-only, optional --prune, image_tag.
- Replace .containerignore with .dockerignore.
- Add the opt-in image prune to the hops role.
- Tag the Caddyfile task so --skip-tags caddy works before DNS cutover.
- Trim comments and rewrite build and deploy text in plain prose.

ansible/roles/caddy/tasks/main.yaml

@@ -1,16 +1,9 @@
 ---
-# Append Hops n Grains' site blocks to the shared Caddyfile.
-#
-# The Caddyfile is a bind mount into the Caddy container, so Caddy sees the
-# change as soon as the file is written; the handler only asks Caddy to re-read
-# it. That is a reload, not a restart, so the other hosted sites are untouched.
-#
-# blockinfile is idempotent on its own via the marker, so there is no need to
-# slurp the file and compare first — which also matters because slurp *fails*
-# when the Caddyfile does not exist yet, on a host where caddy/playbook.yml has
-# not run.
+# Append the site blocks to the shared Caddyfile. The file is bind-mounted into
+# Caddy, so the reload handler is enough. blockinfile is idempotent.
 
 - name: "Add the {{ host }} site blocks to the Caddyfile"
+  tags: [caddy]
   ansible.builtin.blockinfile:
     path: "{{ caddyfile_path }}"
     marker: "# {mark} Ansible managed Caddy snippet for {{ host }}"