JFJochXFELReader: the positional-read handles are held for the most recent files only

The direct chunk read opened one HDF5ImageSource::RawFile per file and never released it, so the
MAX_OPEN_FILES bound on the HDF5 handles did not hold for that path: a dataset stored one frame per
file would keep a descriptor per file open. They now follow the same least-recently-used bound; a
reading thread still holding a released handle keeps it through its shared_ptr.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu

reader/JFJochXFELReader.cpp

@@ -84,6 +84,7 @@ std::shared_ptr<const HDF5ImageSource::RawFile> JFJochXFELReader::RawFileAt(size
     if (raw_files_.size() != files_.size()) {
         raw_files_.assign(files_.size(), nullptr);
         user_block_.assign(files_.size(), 0);
+        raw_order_.clear();
     }
     if (!raw_files_[file]) {
         const hid_t fcpl = H5Fget_create_plist(FileAt(file).GetID());
@@ -97,6 +98,11 @@ std::shared_ptr<const HDF5ImageSource::RawFile> JFJochXFELReader::RawFileAt(size
             throw JFJochException(JFJochExceptionCategory::InputParameterInvalid, "Cannot open " + files_[file]);
         raw_files_[file] = raw;
         user_block_[file] = user_block;
+        raw_order_.push_back(file);
+        if (raw_order_.size() > MAX_OPEN_FILES) {
+            raw_files_[raw_order_.front()].reset();
+            raw_order_.erase(raw_order_.begin());
+        }
     }
     return raw_files_[file];
 }
@@ -718,6 +724,7 @@ void JFJochXFELReader::Close() {
     open_files_.clear();
     raw_files_.clear();
     user_block_.clear();
+    raw_order_.clear();
     files_.clear();
     frames_.clear();
     dataset_.reset();