◇ Could this help me?
Yes. Writing down architectural intent, ownership, permitted dependencies and invariants is long-standing engineering practice, and it matters more with a coding agent that can read every file but cannot tell which dependencies are deliberate and which are accidents. The stop rule is the strongest part: an agent that surfaces a boundary conflict instead of quietly routing around it prevents the slow architectural drift that is expensive to reverse later. General practice.
Read this codebase and draft an ARCHITECTURE.md that answers six questions rather than listing files: what exists (the high-level system map), who owns what (each component's responsibility), what may depend on what (the layer boundaries plus the explicitly forbidden paths), how data moves (the critical end-to-end flows), what must stay true (the architectural invariants), and when to stop (if a task requires breaking a boundary, stop, explain the conflict, show the impact, and propose the smallest change). Keep it to intent and boundaries rather than a file tour, and flag anything in the current code that already violates the invariants you identify.