refactor(caddy): split vhosts into conf.d snippets (core/static/mirror)

Base Caddyfile now imports conf.d/*.caddy. Snippets are mounted selectively
so the stack runs with or without the static site / air-gap mirror:
  00-core   auth + packwiz (always)
  10-static apex landing + launcher downloads
  20-mirror air-gap upstream hosts (tls internal)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

caddy/Caddyfile

@@ -1,40 +1,12 @@
-# auto_https off would disable TLS entirely, breaking `tls internal` for the
-# air-gap mirror vhosts. disable_redirects keeps the apex/auth/packwiz sites
-# plaintext on :80 (they use explicit http://) while still allowing internal
-# TLS on the mirror hosts below.
+# Base Caddy config. Vhosts live in conf.d/*.caddy snippets that are mounted
+# in selectively so the stack can run with or without the static site / mirror:
+#   conf.d/00-core.caddy    auth + packwiz   (always — core ingress)
+#   conf.d/10-static.caddy   apex landing + launcher downloads   (static toggle)
+#   conf.d/20-mirror.caddy   air-gap upstream mirror (tls internal)   (mirror toggle)
+# auto_https disable_redirects: http:// sites stay plaintext on :80; the mirror
+# snippet's hosts still get internal TLS on :443 when that snippet is present.
 {
 	auto_https disable_redirects
 }
 
-http://{$BASE_DOMAIN} {
-	# Launcher downloads live in a sibling mount (not nested under /srv/www,
-	# which is a read-only mount → can't create a nested mountpoint).
-	# handle_path strips the /launcher prefix before serving /srv/launcher.
-	handle_path /launcher/* {
-		root * /srv/launcher
-		file_server browse
-	}
-	handle {
-		root * /srv/www
-		file_server
-	}
-}
-
-http://auth.{$BASE_DOMAIN} {
-	reverse_proxy drasl:25585
-}
-
-http://packwiz.{$BASE_DOMAIN} {
-	root * /srv/pack
-	file_server browse
-}
-
-# Full client air-gap mirror (see plan/11-full-airgap-mirror.md): byte-exact
-# copies of the real upstream hosts served over HTTPS with Caddy's local CA.
-# dnsmasq spoofs these hostnames -> our host; the {host} placeholder roots each
-# hostname at its own mirror subtree. Guests import the Caddy root CA once.
-meta.prismlauncher.org, piston-meta.mojang.com, piston-data.mojang.com, libraries.minecraft.net, maven.neoforged.net, resources.download.minecraft.net {
-	tls internal
-	root * /srv/mirror/{host}
-	file_server
-}
+import /etc/caddy/conf.d/*.caddy

caddy/conf.d/00-core.caddy

@@ -0,0 +1,9 @@
+# Core ingress — always mounted. Drasl auth + packwiz pack metadata.
+http://auth.{$BASE_DOMAIN} {
+	reverse_proxy drasl:25585
+}
+
+http://packwiz.{$BASE_DOMAIN} {
+	root * /srv/pack
+	file_server browse
+}

caddy/conf.d/10-static.caddy

@@ -0,0 +1,14 @@
+# Static toggle — apex landing page + launcher downloads.
+# Mounted only when the stack runs with static files (build-stack.sh up static|full).
+http://{$BASE_DOMAIN} {
+	# Launcher downloads are a sibling mount (/srv/launcher), not nested under
+	# the read-only /srv/www. handle_path strips the /launcher prefix.
+	handle_path /launcher/* {
+		root * /srv/launcher
+		file_server browse
+	}
+	handle {
+		root * /srv/www
+		file_server
+	}
+}

caddy/conf.d/20-mirror.caddy

@@ -0,0 +1,9 @@
+# Mirror toggle — full client air-gap mirror (see plan/11-full-airgap-mirror.md).
+# Byte-exact copies of the real upstream hosts over HTTPS with Caddy's local CA.
+# dnsmasq spoofs these hostnames -> our host; {host} roots each at its subtree.
+# Mounted only when the stack runs with the mirror (build-stack.sh up mirror|full).
+meta.prismlauncher.org, piston-meta.mojang.com, piston-data.mojang.com, libraries.minecraft.net, maven.neoforged.net, resources.download.minecraft.net {
+	tls internal
+	root * /srv/mirror/{host}
+	file_server
+}