Sideways HBM research targets AI memory's thermal ceiling

The reported V-Die and MOSAIC concepts point at a real constraint in HBM scaling: heat removal becomes harder as stacks grow denser and bandwidth rises. These designs are research-stage rather than near-term production plans, so they should not be treated as a capacity forecast. Still, they are relevant for the HBM roadmap because alternatives to TSV-heavy vertical stacks could influence how suppliers attack performance and thermals after current HBM3E and HBM4 generations.