derive: RADGRAM2 header is magic,k,rank,rows,domain (28 B)

scripts/derive-protected-experts.py

@@ -37,8 +37,7 @@ NAME_RE = re.compile(r"^gram\.r(\d)\.blk\.(\d+)\.ffn_down_exps\.(\d+)\.bin$")
 def read_gram(path):
     """(k, rank, rows, trace) from a RADGRAM2 file (full matrix on disk)."""
     with open(path, "rb") as f:
-        hdr = f.read(32)
+        magic, k, rank, rows, domain = struct.unpack("<8sIIQI", hdr[:28])
-        magic, k, rank, rows, domain = struct.unpack("<8sIIIQI", hdr[:32])
         if magic != b"RADGRAM2":
             raise SystemExit(f"not a RADGRAM2 file: {path}")
         n = k * k