Kudzu 0.8.48 - Multi-handler setter callbacks

Kudzu 0.8.48 lets one compiler-specialized setter-callback prop be called once from each of multiple direct intrinsic event handlers. Each call lowers independently to the same parent signal without a callback registry, component runtime, or new browser runtime module. Repeated calls inside one handler, aliases, non-handler uses, forwarding fan-out, and a fourth callback boundary remain source-diagnosed.