Context for processing a batch of leaves in a thread
const LeafBatchContext = struct
const LeafBatchContext = struct {
output_cvs: []align(@alignOf(u64)) u8,
batch_start: usize,
batch_count: usize,
view: *const MultiSliceView,
scratch_buffer: []u8, // Pre-allocated scratch space (no allocations in worker)
total_len: usize, // Total length of input data (for boundary checking)
}