chore: walk the device bundle in fixed-size chunks

Stable clippy rejects `chunks_exact` with a constant size in favour of `as_chunks`, which fails the lint job for the whole workspace, and reading fixed arrays out of the slice drops the length check the old code carried as an `expect`.

core/account/src/directory.rs

@@ -156,12 +156,12 @@ pub fn decode_bundle_payload(payload: &[u8]) -> Result<DecodedBundle, BundleErro
     if body.len() != count * 32 {
         return Err(BundleError::Short);
     }
-    let devices = body
-        .chunks_exact(32)
-        .map(|c| c.try_into().expect("chunks_exact(32) yields 32 bytes"))
-        .collect();
+    let (devices, _) = body.as_chunks::<32>();
 
-    Ok(DecodedBundle { lamport, devices })
+    Ok(DecodedBundle {
+        lamport,
+        devices: devices.to_vec(),
+    })
 }
 
 /// Decode `bundle`, confirm it belongs to `expected_account`, and verify the