fix(io): refuse truncated files in the VOL, async and MPI readers

The truncated-file check and the end-of-file clamp reached File,
LazyFile and MmapFile but not clawhdf5-io's readers, which still opened
truncated files and read past the recorded end of file. NativeVol
(open, and read_dataset for from_bytes), AsyncHDF5File::from_bytes and
MpiVol's collective read now view the file through the new
vol::hdf5_view: from the superblock to Superblock::data_end, refusing a
file shorter than that.

MpiVol's read is compiled only with the mpi-io feature, which needs an
MPI installation; it was not built here. The edit there only swaps its
two-line superblock setup for hdf5_view.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

crates/clawhdf5-io/src/mpi_vol.rs

@@ -180,8 +180,7 @@ fn mpi_collective_read(vol: &MpiVol, location: &str, path: &str) -> Result<Vec<u
     use clawhdf5_format::{
         data_layout::DataLayout, data_read::read_raw_data_full, dataspace::Dataspace,
         datatype::Datatype, filter_pipeline::FilterPipeline, group_v2::resolve_path_any,
-        message_type::MessageType, object_header::ObjectHeader, signature::split_user_block,
-        superblock::Superblock,
+        message_type::MessageType, object_header::ObjectHeader,
     };
     use mpi::traits::*;
 
@@ -193,9 +192,9 @@ fn mpi_collective_read(vol: &MpiVol, location: &str, path: &str) -> Result<Vec<u
 
     if rank == 0 {
         let file = std::fs::read(location).map_err(VolError::Io)?;
-        // Addresses are relative to the superblock: skip any user block.
-        let (_, bytes) = split_user_block(&file).map_err(|e| VolError::DataError(e.to_string()))?;
-        let sb = Superblock::parse(bytes, 0).map_err(|e| VolError::DataError(e.to_string()))?;
+        // From the superblock to the recorded end of file; truncated files
+        // are refused.
+        let (bytes, sb) = crate::vol::hdf5_view(&file)?;
         let addr = resolve_path_any(&bytes, &sb, path)
             .map_err(|e| VolError::NotFound(format!("{path}: {e}")))?;
         let oh = ObjectHeader::parse(&bytes, addr as usize, sb.offset_size, sb.length_size)