test(gate): accept fact/other chunks — validate data chunk ends at EOF

sf.write() float32 WAVs carry a fact chunk; strict 44+data_size check was
too narrow. Walk chunks instead; bridge header bug (half data_size) still
caught because its data chunk must run to EOF.

tests/test_lossless_compliance.py

@@ -41,10 +41,19 @@ def harness_audit_null_test(original_path, rendered_path, threshold_db=THRESHOLD
 
 def wav_format_info(path):
     with open(path, "rb") as f:
-        b = f.read(44)
+        b = f.read()
     assert b[:4] == b"RIFF" and b[8:12] == b"WAVE", "not RIFF/WAVE"
-    data_size = struct.unpack_from("<I", b, 40)[0]
-    assert os.path.getsize(path) == 44 + data_size, "data chunk size mismatch"
+    # Walk chunks: "data" must run exactly to EOF (fact/other chunks allowed).
+    pos = 12
+    data_ok = False
+    while pos + 8 <= len(b):
+        cid = b[pos:pos + 4]
+        size = struct.unpack_from("<I", b, pos + 4)[0]
+        if cid == b"data":
+            assert pos + 8 + size == len(b), "data chunk must end at EOF"
+            data_ok = True
+        pos += 8 + size + (size & 1)  # chunks are word-aligned
+    assert data_ok, "no data chunk"
     return {
         "fmt_tag": struct.unpack_from("<H", b, 20)[0],
         "channels": struct.unpack_from("<H", b, 22)[0],