CI: pin checkout to v7 and setup-go to v7

Both v4/v5 ran their action code on the deprecated Node 20 runtime, which
GitHub was force-migrating to Node 24 with a warning on every run. v7 of each
targets Node 24 natively, removing the deprecation annotations.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: waveriderai

.github/workflows/ci.yml

@@ -10,9 +10,9 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@v7
         with:
           go-version: '1.22'
           check-latest: true
@@ -38,7 +38,7 @@ jobs:
   plugin:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
       - name: Validate plugin manifest
         run: |