Publish llmgw_model_update_available, and alert on it

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

deploy/monitoring/llmgw-rules.yml

@@ -156,6 +156,18 @@ groups:
             llmgw-backup.service` on the control plane says why the last one
             failed; docs/install.md, "Backing up", says how to set it up.
 
+      - alert: ModelUpdateAvailable
+        expr: llmgw_model_update_available == 1
+        for: 1h
+        labels: { severity: info }
+        annotations:
+          summary: "{{ $labels.repo }} has new weights for {{ $labels.model }}"
+          description: >-
+            The registry repository the model was served from has published
+            different files under the same names. `llmgw ctl model updates`
+            lists what changed; `llmgw ctl model update {{ $labels.model }}`
+            moves it to them, and `llmgw ctl model rollback` goes back.
+
       - alert: PoolSaturated
         expr: llmgw_pool_saturation > 1
         for: 5m

internal/cli/server.go

@@ -184,8 +184,8 @@ func newServerCmd() *cobra.Command {
 				if err := rt.RegisterMetrics(fleetmetrics.New(ctl)); err != nil {
 					return err
 				}
-				// Whether models' repositories have new weights; filled in
-				// once the mirror is set up, below.
+				// Whether models' repositories have new weights; given its
+				// source once the mirror is set up, below.
 				if err := rt.RegisterMetrics(updateMetrics); err != nil {
 					return err
 				}