A02: Fix double cooldown reservation bug in main()

Bug: main() called both enforce_fetch_interval() and mark_fetch(), which
both now call check_and_reserve(). On cold start:
  1. enforce_fetch_interval() → check_and_reserve() → SUCCESS (reserves)
  2. mark_fetch() → check_and_reserve() → FAILS (cooldown now active)

This prevented HTTP from ever being called on cold start.

Fix:
- Removed duplicate calls to enforce_fetch_interval() and mark_fetch()
- Single check_and_reserve() call before fetch_html()
- enforce_fetch_interval() and mark_fetch() remain as legacy wrappers

Verification:
- All 18 community_cli tests pass
- Code analysis confirms single check_and_reserve() call in main()
- check_and_reserve() is atomic with exclusive lock for check+reserve

rf4_research/community_cli.py

@@ -275,9 +275,8 @@ def main(argv: list[str] | None = None) -> int:
     url = args.url or default_url
     try:
         site_key = fetch_site_key(url)
-        enforce_fetch_interval(site_key, state_file=args.state_file)
-        # Reserve before network I/O: failed attempts count toward the limit too.
-        mark_fetch(site_key, state_file=args.state_file)
+        # Single atomic check-and-reserve before network I/O: failed attempts count toward the limit too.
+        check_and_reserve(site_key, state_file=args.state_file)
         html = fetch_html(url)
         records = (parse(html, source_url=url) if args.source in DETAIL_SOURCES else parse(html))[:args.limit]
     except Exception as exc: