Template
The structure every package page follows.
Every package gets docs/packages/<name>.md with this structure. Keep it short;
the API reference lives on docs.rs, not here.
# <name>
One sentence: what the package computes and what it does not.
## Status
Version, registry, who uses it. Honest about anything half-built.
## Structure
One Mermaid diagram: data flow or modules. Do not repeat the graph from
architecture.md; show the inside of this package.
## Public surface
The few types and functions a consumer needs, with one sentence each. Link to
docs.rs for the rest.
## Dependencies
Downward: which packages this one needs. Upward: who uses it.
## Limits
What the package does not decide, does not prove, does not see. This section
is mandatory — it prevents claims the data cannot support.