core: Instructions file for Codex

@epicurrents/core — architecture notes for AI coding assistants

@epicurrents/core is the dependency root of the Epicurrents package family. It defines the application entry point (Epicurrents), the runtime state manager, the asset/resource/module/service abstractions, the biosignal montage and trend machinery, the worker commission protocol, and the shared TypeScript types every sibling package imports. Every other @epicurrents/* package — readers, modality modules, services, and the viewer interface — builds on the contracts defined here, so a change in this package can break all of them at once.

This file is the in-depth technical reference for AI coding assistants: internal architecture, the contracts the package guarantees to consumers, and the gotchas that bite when editing it. It should let an agent answer most questions about the package directly, or at least point at the right place to look. README.md is the denser user-facing description (structure, usage, build workflow) and the right link to hand a human; ROADMAP.md carries design intent, not current state. Sibling packages (readers, modules, services, interface) keep their own AGENTS.md; module-side and rendering-side detail lives there, not here.

Keep this file current — update it in the same change set as the code. This document only works if it describes the code as it is; a stale section is worse than a missing one, because an agent will act on it. After any change that alters something documented here — a contract, a protocol shape, a lifecycle, a public symbol, a limitation being lifted — update the affected section (or add one for a new subsystem) before reporting the work done. The same rule applies to the siblings: README.md when the user-facing surface (usage, structure, build workflow) changes, ROADMAP.md when documented deferred work lands or new work is deliberately deferred. Pure refactors, test-only changes and bug fixes that restore documented behaviour need no update.