Split host setup into explicit entity actions

actions/config/cron.py

@@ -0,0 +1,14 @@
+# actions/config/cron.py
+"""Port of config/cron — install crontab from configs/cron/crontab."""
+import os
+from engine.descriptor import Meta, Flag
+
+METADATA = Meta(summary="Install the node crontab from configs/cron/crontab.",
+                args=[Flag("--dry-run", "Render + preview; do not install.")])
+
+def run(ctx, args):
+    crontab = os.path.join(ctx.paths.configs, "cron", "crontab")
+    if not os.path.isfile(crontab):
+        ctx.log.error(f"Crontab file not found: {crontab}"); raise SystemExit(1)
+    text = ctx.tpl.render(crontab, ctx.vars())
+    ctx.host.install_crontab(text, dry_run=args.dry_run)