fix: replace grep-based integrity check with reliable Python verification

The previous grep-based null byte detection was producing false positives
in the GitHub Actions environment. Files like 2151220-passwords.txt were
incorrectly flagged as corrupted when they contained zero null bytes.

Changes:
- Replaced shell grep command with Python-based integrity verification
- Uses Python's binary file reading for accurate null byte detection
- Verified locally: 70/70 files pass (0 null bytes detected)
- More reliable across different shell environments

The new check:
✓ Properly detects actual binary corruption (null bytes)
✓ Works consistently across platforms
✓ Provides clear error messages with file paths
✓ No false positives

Tested locally with Python verification - all files are clean.

Author: duyetbot

.github/workflows/validate.yml

@@ -94,17 +94,48 @@ jobs:
     - name: Checkout repository
       uses: actions/checkout@v4
 
+    - name: Set up Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: '3.11'
+
     - name: Verify file integrity
       run: |
         echo "🔐 Verifying file integrity..."
-
-        # Check for null bytes (corruption indicator)
-        if find . -type f \( -name "*.txt" -o -name "*.lst" \) ! -path "./.git/*" -exec grep -l $'\x00' {} \; 2>/dev/null | head -5; then
-          echo "✗ Corrupted files detected (null bytes found)"
-          exit 1
-        else
-          echo "✓ No corrupted files detected"
-        fi
+        python3 << 'PYTHON_SCRIPT'
+        import os
+        import sys
+        from pathlib import Path
+
+        corrupted = []
+        checked = 0
+
+        for ext in ['*.txt', '*.lst']:
+            for filepath in Path('.').rglob(ext):
+                if '.git' in filepath.parts:
+                    continue
+
+                checked += 1
+                try:
+                    with open(filepath, 'rb') as f:
+                        content = f.read()
+                        # Check for null bytes (binary corruption)
+                        if b'\x00' in content:
+                            corrupted.append(str(filepath))
+                except Exception as e:
+                    print(f"⚠️  Error reading {filepath}: {e}")
+                    corrupted.append(str(filepath))
+
+        print(f"Checked {checked} files")
+
+        if corrupted:
+            print(f"✗ Corrupted files detected ({len(corrupted)}):")
+            for f in corrupted[:10]:
+                print(f"  - {f}")
+            sys.exit(1)
+        else:
+            print("✓ No corrupted files detected")
+        PYTHON_SCRIPT
 
     - name: Check line endings
       run: |