Decode the Items Next Action Indicator (TS 102 223 §8.24)

- tag '18' (TS 101 220: "18 only"): one byte per item, §9.4 coding;
  '00' and reserved values mean "no next action" (decoded to None)
- items[] now carry a per-item next_action; a list whose length differs
  from the item count is preserved raw (spec requires X = item count)
- detail view renders "Item 0xNN: text → COMMAND"; the APDU-list summary
  is unchanged — next actions are detail-only, as requested
- tests: 3 real SET UP MENU samples (local sessions 47/53/57) + a
  length-mismatch tolerance case
- v2.1.2; SW cache simtrace-analyser-v57

tests/test_pcap_import.py

@@ -224,7 +224,7 @@ class TestImportEndpoint(unittest.TestCase):
 class TestVersion(unittest.TestCase):
     def test_package_version(self):
         from simtrace2_pysniff import __version__
-        self.assertEqual(__version__, '2.1.1')
+        self.assertEqual(__version__, '2.1.2')
 
     def test_status_includes_version(self):
         import os