ci: fix workflow-linter YAML parse error + self-flag bug

Combined fix:
  1. The 'Add permissions...' multi-line echo on the old version had
     a YAML literal-block indentation bug that crashed the workflow
     file parser ('This run likely failed because of a workflow file
     issue'). Collapsed to a single-line echo.
  2. The action-pinning grep matched its own source line in the
     workflow ('grep -rn "uses:"' contains 'uses:'). Anchored to
     '^[[:space:]]+uses:' so it only matches workflow `uses:` lines.

Together these two changes restore workflow-linter from a permanent
failure state across the estate.

Author: hyperpolymath

.github/workflows/workflow-linter.yml

@@ -54,8 +54,7 @@ jobs:
             fi
           done
           if [ $failed -eq 1 ]; then
-            echo "Add 'permissions:
-  contents: read' at workflow level"
+            echo "Add a top-level 'permissions:' block (e.g. {contents: read})"
             exit 1
           fi
           echo "All workflows have permissions declared"