cubelinux: the digest's byte count is the store's, not the reader's

'bytes=' reported how much had been read, so the same records disagreed between a
file (16,537,532) and a device slot holding them (67,108,864). The gates compare
this line, so it has to mean the same thing on both sides: it is now the header plus
the records — the length the store actually is.

Found by moving the machine's real store into a device store and comparing.

drivers/cube/cubelinux_store.rs

@@ -325,12 +325,12 @@ fn digest(image: &[u8]) -> Line {
     let mut count: u64 = 0;
     let mut value_bytes: u64 = 0;
     let mut errors: u64 = 0;
-    let mut off = layout.image_off
-        + if header.version == VERSION_V1 {
-            HEADER_LEN_V1
-        } else {
-            HEADER_LEN_V2
-        };
+    let header_len = if header.version == VERSION_V1 {
+        HEADER_LEN_V1
+    } else {
+        HEADER_LEN_V2
+    } as u64;
+    let mut off = layout.image_off + header_len as usize;
     let mut remaining = header.record_count;
     let end = layout.image_off + end;
 
@@ -388,7 +388,11 @@ fn digest(image: &[u8]) -> Line {
         "digest version={} curve={} bytes={} records={} value_bytes={} fnv1a64={:016x} errors={}",
         header.version,
         header.curve,
-        image.len(),
+        // `bytes` is a property of the store, not of how it was read: the header plus the
+        // records, whatever padding the reader happened to see. Reporting what was read made
+        // the same records disagree between a file and a device — and the gates compare this
+        // line, so it has to mean the same thing on both sides.
+        header_len + count * RECORD_FIXED as u64 + value_bytes,
         count,
         value_bytes,
         h,