The one naming rule, shared with the emitter.

protoc-gen-clojure kebab-cases proto field names into record fields and map
keys with exactly this algorithm (its `field-key-symbol`). The runtime's
generic nested-map path must produce the same keys byte for byte, or records
built by generated code and maps built by the runtime stop being
interchangeable. Any change here is a wire-compatibility break with every
generated file in existence — don't.

Kebab-casing is lossy (STYLE_LEGACY files can mix conventions), which is why
the emitted `rt/field` lookups carry the exact proto name and this fn is used
only for the Clojure-side keys.