PFM-TASK-7777: Update dependabot configuration for GitHub Actions.

Author: Benno42

.github/dependabot.yml

@@ -1,6 +1,62 @@
 version: 2
 updates:
+  # Default branch (master)
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
       interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+
+  # Active release branches (release/25.2 → release/26.2)
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    target-branch: "release/25.2"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    target-branch: "release/25.3"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    target-branch: "release/25.4"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    target-branch: "release/26.1"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    target-branch: "release/26.2"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"

README.md

@@ -11,5 +11,6 @@ JavaScript action runtime since June 2026).
 - Self-hosted runners must run GitHub Actions Runner **>= 2.327.1**.
 - `.npmrc` provisioning uses the in-repo composite `.github/actions/use-npmrc` (input `dot-npmrc`),
   referenced per release branch like all internal composites.
-- `.github/dependabot.yml` keeps the SHA pins current on `master`; release branches are backported
-  manually.
+- `.github/dependabot.yml` keeps the SHA pins current on `master` and the active release branches
+  (`release/25.2` through `release/26.2`) via per-branch `target-branch` entries; each branch gets
+  one grouped Action-update PR per week.