Enable Renovate automerge for non-major RIE dependency bumps

Automerge non-major gomod bumps (minor/patch), Go-toolchain bumps, and
non-major GitHub Actions updates so Go-dep/stdlib CVE fixes land without
manual review. Security updates get their own ungrouped, automerged path
via vulnerabilityAlerts so a CVE fix is never blocked behind the grouped
batch. Majors stay manual (automerge explicitly set to false).

Automerge still waits for green CI before merging.

Author: carole-lavillonniere

renovate.json

@@ -4,24 +4,43 @@
     "config:recommended"
   ],
   "postUpdateOptions": ["gomodTidy"],
+  "platformAutomerge": true,
   "packageRules": [
     {
       "matchManagers": ["gomod"],
       "matchDepTypes": ["golang"],
       "rangeStrategy": "bump",
-      "groupName": "Go toolchain"
+      "groupName": "Go toolchain",
+      "automerge": true
     },
     {
       "matchManagers": ["gomod"],
       "excludePackageNames": ["go"],
       "matchUpdateTypes": ["minor", "patch"],
-      "groupName": "Go dependencies (non-major)"
+      "groupName": "Go dependencies (non-major)",
+      "automerge": true
     },
     {
       "matchManagers": ["gomod"],
       "excludePackageNames": ["go"],
       "matchUpdateTypes": ["major"],
-      "enabled": false
+      "enabled": false,
+      "automerge": false
+    },
+    {
+      "matchManagers": ["github-actions"],
+      "matchUpdateTypes": ["minor", "patch", "digest"],
+      "automerge": true
+    },
+    {
+      "matchManagers": ["github-actions"],
+      "matchUpdateTypes": ["major"],
+      "automerge": false
     }
-  ]
+  ],
+  "vulnerabilityAlerts": {
+    "groupName": null,
+    "automerge": true,
+    "labels": ["security"]
+  }
 }