New file: src/assemblers/node_based_coo.jl
Features:
- assemble! implementation for nodal assembly
- Assembles contributions node-by-node instead of element-by-element
- Uses node_to_elements connectivity
- Accumulates blocks for all elements touching each node
Architecture:
- Outer loop over nodes (not elements)
- Inner loop over elements containing each node
- Natural for contact mechanics (contact is nodal)
Status: Experimental, proof-of-concept implementation.
Not yet optimized like element-based assembly.
Jukka Aho