gen

Instruction file imported from webern/mx (.github/instructions/gen.instructions.md). Copyright stays with the author.

gen/ is a Python code generator (XSD -> IR -> Plates -> Mustache press) with four targets: C++ (gen/cpp, the product), Go, C, JSON Schema. Review against its cardinal rules (gen/AGENTS.md):

• Language-agnosticism: no language knowledge in any *.py outside a target's own directory. Reject language tables, per-language branches, or target-name checks in generator Python; language facts belong in the target's config.toml and templates/.
• The IR is a pure function of the XSD: no configurable knobs in gen/ir/ (the sounds.xml fold is the one documented exception).
• Templates stay dumb: naming/structural decisions belong in Plates or press context, not in template text. The Mustache engine has no expressions or filters -- reject attempts to add logic to it.
• Fail loud: new error paths must exit non-zero with a template:line style message, never emit best-effort output.
• Generated output is committed: a generator change without its regenerated output (or vice versa) fails the CI drift check (make gen then git diff --exit-code).
• Template identifiers must be unity-build safe: use {{ident}}-suffixed names for file-local symbols.