File System as Object — Directories, Interfaces, and the UPPERCASE Marker Grammar

"A directory named <things>/ is saying: the things in here are of the type <thing>. A file named FOO.md at a directory's root is saying: this directory exports the FOO interface. The directory IS an implementation class; the UPPERCASE marker files ARE its interface declarations; no UUIDs needed because the filename IS the class name."

This skill formalizes a grammar that already exists throughout MOOLLM. Every skill you've read — skill, prototype, card, schema, adventure, room, character, incarnation — uses these rules implicitly. The other meta-skills USE the grammar; this skill NAMES it so newcomers (human or LLM) can read MOOLLM directory trees fluently without pattern-matching each one from scratch.

The Three Rules

Rule 1: Plural-named directories declare element type

A directory named <things>/ declares "the things in here are of type <thing>."