docs/architecture.md: layering, service map, event taxonomy, the
session/turn/step lifecycle, Cordis waterfall semantics, an extension
cookbook, the plugin sanity checklist mapping every MVP feature to its
extension mechanism, and the deferred-work TODO list (sub-agents,
persistence backends, compaction, DeepSeek V4 adapter, parallel tool
execution, streaming-protocol review).
AGENTS.md: repo layout, commands, conventions (dsh-* naming, ESM,
effect-based registrations, declaration merging, waterfall semantics),
and the vendoring policy pointer.
