Kiln's code conventions and per-area gotchas, plus a diff gate that enforces the mechanical ones. Invoke before writing or changing any Python, TypeScript or Svelte code in the Kiln repo (libs/core, libs/server, app/desktop, app/web_ui), and when reviewing such a change. Covers comments, startup and entry points, globals and module state, config reads, module layering, library-vs-app rules and async I/O.