VariableId.h header

using ew::core::foundation::VariableId = Id<VariableIdTag>

Stable, globally-unique identity for a story variable.

A branching condition references the variable it tests by THIS, never by its name. The name is what the author types and therefore what the author renames – and a condition storing the name would break silently the moment they did, which is exactly the defect the A3 audit found in the audience registry and had to repair afterwards. The name is resolved to an id at the boundary where a person types it, the way MCP tools already resolve object names.