fix(grafana): set explicit 2m interval on CPU query targets

- Global CPU Usage: set interval="2m" on Real Linux/Windows targets
- CPU Usage: set interval="2m" on Real Linux/Windows targets
- Previously empty interval caused $__rate_interval mismatch

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

grafana/dashboards/main.json

@@ -150,7 +150,7 @@
           "exemplar": true,
           "expr": "avg(sum by (instance, cpu) (rate(node_cpu_seconds_total{mode!~\"idle|iowait|steal\", cluster=\"$cluster\", job=\"$job\"}[$__rate_interval])))",
           "hide": false,
-          "interval": "",
+          "interval": "2m",
           "legendFormat": "Real Linux",
           "range": true,
           "refId": "Real Linux"
@@ -164,7 +164,7 @@
           "exemplar": true,
           "expr": "avg(sum by (core) (rate(windows_cpu_time_total{mode!=\"idle\", cluster=\"$cluster\"}[2m])))",
           "hide": false,
-          "interval": "",
+          "interval": "2m",
           "legendFormat": "__auto",
           "range": true,
           "refId": "Real Windows"
@@ -820,7 +820,7 @@
           "editorMode": "code",
           "exemplar": true,
           "expr": "sum(rate(node_cpu_seconds_total{mode!~\"idle|iowait|steal\", cluster=\"$cluster\", job=\"$job\"}[$__rate_interval])) or vector(0)",
-          "interval": "",
+          "interval": "2m",
           "legendFormat": "Real Linux",
           "range": true,
           "refId": "Real Linux"
@@ -834,7 +834,7 @@
           "exemplar": true,
           "expr": "sum(rate(windows_cpu_time_total{mode!=\"idle\", cluster=\"$cluster\"}[$__rate_interval])) or vector(0)",
           "hide": false,
-          "interval": "",
+          "interval": "2m",
           "legendFormat": "Real Windows",
           "range": true,
           "refId": "Real Windows"