Change details: the length cut never hides observed bytes (v2.7.5)

- a record whose FCP understates the layout (the reported case: record_len 2
  while the READ RECORD carried P3=0x2C and returned 44 bytes) had its rows
  cut to two cells by the v2.7.3 length rule, hiding 42 newly-observed bytes
  while the summary still counted them
- the filler now stops at the known length only while the data fits inside
  it; beyond that — and when the length is unknown or absent — the row ends
  at the data, so nothing observed is ever hidden and no bytes are invented
- verified on the live payload (session 55, 5f3a/4f09 change 0): before = 2
  cells, both changed; after = 16+16+12 cells with 2 changed and 42 newly
  observed, matching the summary line
- tests: the regression case (a 2-byte record_len with a 44-byte read) and
  the unknown-length case, whose row now ends at the data; 527 Python +
  76 Node tests
- PWA_VERSION/pyproject/version.py 2.7.5, SW cache simtrace-analyser-v85

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__, '2.7.4')
+        self.assertEqual(__version__, '2.7.5')
 
     def test_status_includes_version(self):
         import os