fix: suppress SC1091 in test and upgrade checkout@v5

- Add shellcheck disable=SC1091 for dynamic source in bats test
  (file is created at runtime, ShellCheck cannot follow the path)
- Upgrade actions/checkout@v4 → @v5 to fix Node.js 20 deprecation
  (GitHub will force Node.js 24 on June 16, 2026)

Author: morphilab

.github/workflows/test.yml

@@ -11,7 +11,7 @@ jobs:
     name: ShellCheck
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Run ShellCheck (all .sh and .bats files)
         run: |
@@ -24,7 +24,7 @@ jobs:
     name: Bats Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install dependencies
         run: |

test/test_theduckpurge.bats

@@ -194,6 +194,7 @@ teardown() {
 }
 
 @test "library mode: sourcing exposes functions" {
+    # shellcheck disable=SC1091
     source "$TEST_TMP/theduckpurge"
     command -v check_metadata
     command -v clean_file