* feat(entity/search): add LinearPool/BlockHeap, split contiguous entity layout and add direct-pointer fast search path
Introduce single-heap candidate structures (LinearPool/BlockHeap) and
refactor greedy search to dispatch between pool and dual-heap paths.
Split node layout into separate vector/graph arrays for better cache
locality, add zero-copy get_vector_ptr() on the hot path, and extract
huge-page allocation into MemoryHelper. Also adds pyglass attribution.
luoxiaojian