deploy, docs: turn service_down back on (V-444)

It was disabled because it could not say which service. It can now.

deploy/mavend.json

@@ -8,12 +8,12 @@
   "//disabled_rules": [
     "Nudge rules that are not wired at all. Names come from loop.DefaultRules:",
     "water, meal, break, service_down, netdata_critical.",
-    "service_down is off because it cannot say WHICH service — mavpoll folds the",
-    "whole kuma gauge into one boolean, so the nudge is always the generic 'a",
-    "service on homesrv is down'. Nothing to act on, every fifteen minutes.",
-    "Turn it back on once Vikunja #444 lands a fact per monitor."
+    "service_down is back on: mavpoll now writes one fact per kuma monitor",
+    "(service_down:<name>), so the nudge names the service and pausing a monitor",
+    "in kuma silences that monitor. It is also edge-triggered, so a service that",
+    "stays down is one nudge, not one every fifteen minutes."
   ],
-  "disabled_rules": ["service_down"],
+  "disabled_rules": [],
 
   "phraser": {
     "model_path": "/opt/maven/models/llm/qwen3/Qwen3-1.7B-UD-Q4_K_XL.gguf",