Zener Language

If you're working with Zener HDL files, load this before touching any `.zen` code. It covers the full language semantics: module loading and instantiation, the `io()` and `config()` API patterns, net types and power domains, component sourcing with proper symbol metadata, physical units and E-series snapping, and the critical DNP workflow where you instantiate everything and toggle population state instead of conditionally adding circuits. The authoring guidance is opinionated and practical, things like keeping power rails explicit, exposing meaningful configs rather than implementation details, and avoiding decorative comments. It also reminds you to preserve those trailing `# pcb:sch` annotations and check the pcb CLI changelog for recent changes.