chore: add validation script for GitHub Actions composite actions

- Introduced a new script, `validate-actions.sh`, to validate the structure of GitHub Actions composite actions, ensuring required fields are present and correctly configured.
- The script checks for the existence of action files, required fields, and proper references in the CI workflow, enhancing the reliability of CI processes.

Benefits:
- Improves the integrity of GitHub Actions by automating validation checks, reducing the likelihood of misconfigurations.
- Streamlines the CI workflow by ensuring that all actions are correctly defined and referenced before execution.

.github/scripts/validate-actions.sh

@@ -0,0 +1,84 @@
+#!/bin/bash
+# Validate GitHub Actions composite action structure
+
+set -e
+
+echo "Validating GitHub Actions composite actions..."
+
+ACTIONS_DIR=".github/actions"
+REQUIRED_FIELDS=("name" "description" "runs")
+
+validate_action() {
+    local action_file="$1"
+    local action_name=$(basename $(dirname "$action_file"))
+    
+    echo "Checking $action_name..."
+    
+    # Check if file exists
+    if [ ! -f "$action_file" ]; then
+        echo "  ✗ action.yml not found"
+        return 1
+    fi
+    
+    # Check required fields
+    for field in "${REQUIRED_FIELDS[@]}"; do
+        if ! grep -q "^${field}:" "$action_file"; then
+            echo "  ✗ Missing required field: $field"
+            return 1
+        fi
+    done
+    
+    # Check for 'using: composite'
+    if ! grep -q "using: 'composite'" "$action_file"; then
+        echo "  ✗ Not marked as composite action"
+        return 1
+    fi
+    
+    echo "  ✓ Valid composite action"
+    return 0
+}
+
+# Validate all actions
+all_valid=true
+for action_yml in "$ACTIONS_DIR"/*/action.yml; do
+    if ! validate_action "$action_yml"; then
+        all_valid=false
+    fi
+done
+
+# Check that CI workflow references actions correctly
+echo ""
+echo "Checking CI workflow..."
+CI_FILE=".github/workflows/ci.yml"
+
+if [ ! -f "$CI_FILE" ]; then
+    echo "  ✗ CI workflow not found"
+    all_valid=false
+else
+    # Check for checkout before action usage
+    if grep -q "uses: actions/checkout@v4" "$CI_FILE"; then
+        echo "  ✓ Repository checkout step present"
+    else
+        echo "  ✗ Missing checkout step"
+        all_valid=false
+    fi
+    
+    # Check for composite action references
+    action_refs=$(grep -c "uses: ./.github/actions/" "$CI_FILE" || echo "0")
+    if [ "$action_refs" -gt 0 ]; then
+        echo "  ✓ Found $action_refs composite action references"
+    else
+        echo "  ✗ No composite action references found"
+        all_valid=false
+    fi
+fi
+
+echo ""
+if [ "$all_valid" = true ]; then
+    echo "✓ All validations passed!"
+    exit 0
+else
+    echo "✗ Some validations failed"
+    exit 1
+fi
+