fix: rename tautological test to honest roundtrip

test_header_decode_wraps_struct_error claimed to test struct.error
wrapping but actually performed a successful roundtrip on valid
data. The struct.error path in Header.decode is unreachable because
the length check fires first. Rename to test_header_roundtrip_minimal
to honestly describe what the test exercises.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

tests/test_codec.py

@@ -158,16 +158,10 @@ def test_header_decode_empty_raises_decode_error(self) -> None:
         with pytest.raises(DecodeError):
             Header.decode(b"")
 
-    def test_header_decode_wraps_struct_error(self) -> None:
-        """Header.decode should wrap struct.error in DecodeError for consistency.
-
-        Header.encode wraps struct.error in EncodeError. Header.decode should
-        do the same with DecodeError, even though the length check makes
-        struct.error unlikely in practice.
-        """
+    def test_header_roundtrip_minimal(self) -> None:
+        """Minimal header with msg_type=0 and schema=0 roundtrips."""
         from dqlitewire.messages.base import Header
 
-        # Valid length but still exercises the try/except path
         header = Header(size_words=1, msg_type=0, schema=0)
         data = header.encode()
         decoded = Header.decode(data)