grafana: count log lines that arrive with no severity

The mapping above needs something that says whether it is still working
after whoever wrote it has gone. A timeseries rather than a stat, so a
regression is a line lifting off zero rather than a number nobody reads.

Two series, and the split is the point: rows that carried a PRIORITY and
arrived with no severity anyway (a broken mapping — this one must reach
zero and stay there), against rows that never had a priority to map. The
latter is Claude Code's own OTLP telemetry, which emits log records with no
severity set at the source; mapping cannot reach it, so it is named rather
than folded into one number that never goes to zero.

Needs no provisioning change — logstore.json is already in the shipped
dashboard list.

nix/host-modules/swarm-grafana/dashboards/logstore.json

@@ -339,7 +339,7 @@
         "h": 12,
         "w": 12,
         "x": 0,
-        "y": 24
+        "y": 33
       },
       "targets": [
         {
@@ -391,7 +391,7 @@
         "h": 12,
         "w": 12,
         "x": 12,
-        "y": 24
+        "y": 33
       },
       "targets": [
         {
@@ -443,7 +443,7 @@
         "h": 9,
         "w": 24,
         "x": 0,
-        "y": 36
+        "y": 45
       },
       "targets": [
         {
@@ -487,6 +487,103 @@
           "sort": "desc"
         }
       }
+    },
+    {
+      "id": 9,
+      "type": "timeseries",
+      "title": "Log rows with no severity (must be zero)",
+      "description": "This panel is a check rather than a view: the collector maps journald's PRIORITY onto an OpenTelemetry severity at every tier, and this is what says out loud whether a line got one. Both series are rows whose `severity_text` is absent or the literal `Unspecified`, which is what VictoriaLogs stores when nothing set a severity — split by whether the row had a PRIORITY to map in the first place.\n\n**`journald_priority_unmapped`** is a row that carries PRIORITY and still arrived without a severity. It is the regression line: nonzero means a journald receiver somewhere lost its severity_parser operator, so read it against `nix/journald-severity.nix` and the two receivers that import it.\n\n**`no_priority_field`** is a row that never had a priority — today that is Claude Code's own OTLP telemetry (`scope.name: com.anthropic.claude_code.events`), which emits log records with no severity set at the source. Mapping cannot reach it; it needs a fix where it is produced, so this series is expected nonzero until that lands and is NOT evidence the mapping broke.\n\nRange-scoped over time on purpose. An instantaneous zero is also what a broken query returns — a line you can watch go to zero and stay there is the part that survives whoever wrote it. To sanity-check the query itself, read it against `Rows in range · all sources (control)` above: that panel nonzero while both of these are flat zero means these queries stopped matching, not that every line grew a severity.",
+      "datasource": {
+        "type": "victoriametrics-logs-datasource",
+        "uid": "@logsDatasourceUid@"
+      },
+      "gridPos": {
+        "h": 9,
+        "w": 24,
+        "x": 0,
+        "y": 24
+      },
+      "targets": [
+        {
+          "refId": "A",
+          "datasource": {
+            "type": "victoriametrics-logs-datasource",
+            "uid": "@logsDatasourceUid@"
+          },
+          "queryType": "statsRange",
+          "expr": "(severity_text:\"\" OR severity_text:\"Unspecified\") PRIORITY:* | stats count() as journald_priority_unmapped"
+        },
+        {
+          "refId": "B",
+          "datasource": {
+            "type": "victoriametrics-logs-datasource",
+            "uid": "@logsDatasourceUid@"
+          },
+          "queryType": "statsRange",
+          "expr": "(severity_text:\"\" OR severity_text:\"Unspecified\") PRIORITY:\"\" | stats count() as no_priority_field"
+        }
+      ],
+      "fieldConfig": {
+        "defaults": {
+          "unit": "short",
+          "decimals": 0,
+          "color": {
+            "mode": "palette-classic"
+          },
+          "custom": {
+            "drawStyle": "line",
+            "lineWidth": 2,
+            "fillOpacity": 10,
+            "showPoints": "never",
+            "spanNulls": false,
+            "axisSoftMin": 0
+          }
+        },
+        "overrides": [
+          {
+            "matcher": {
+              "id": "byName",
+              "options": "journald_priority_unmapped"
+            },
+            "properties": [
+              {
+                "id": "color",
+                "value": {
+                  "mode": "fixed",
+                  "fixedColor": "red"
+                }
+              }
+            ]
+          },
+          {
+            "matcher": {
+              "id": "byName",
+              "options": "no_priority_field"
+            },
+            "properties": [
+              {
+                "id": "color",
+                "value": {
+                  "mode": "fixed",
+                  "fixedColor": "orange"
+                }
+              }
+            ]
+          }
+        ]
+      },
+      "options": {
+        "legend": {
+          "displayMode": "table",
+          "placement": "bottom",
+          "showLegend": true,
+          "calcs": ["max", "lastNotNull"]
+        },
+        "tooltip": {
+          "mode": "multi",
+          "sort": "desc"
+        }
+      }
     }
   ]
 }