fix: audit findings — edge cases in paginate, output, run

- paginate.py: max(nums) on empty set → guard
- paginate.py: HEAD fallback to GET if server doesn't support HEAD
- output.py: disk health check every 500 topics
- run.py: avoid page-1 extra redirect
- __main__.py: URL validation (must contain vwts.ru)

vwts_scraper/output.py

@@ -39,3 +39,11 @@ def save_topic(section_slug: str, section_name: str, topic: dict,
     st["topic_count"] += 1
     log.info(f"      💾 part_{st['file_index']:04d}.jsonl "
              f"({fpath.stat().st_size/1024/1024:.1f} MB)")
+
+    if st["topic_count"] % 500 == 0:
+        # Каждые 500 тем — проверяем что диск ещё жив
+        try:
+            fpath.stat()
+        except OSError as e:
+            log.critical(f"❌ Ошибка диска: {e}")
+            raise