Namespace registry for std/kernel plugin discovery

[ztripez]

Goal

Introduce a compile-time namespace registry so namespaces like kernel and std self-register via static linking (linkme), enabling the compiler to discover available namespaces without hardcoding.

Scope

• Add NamespaceDescriptor and NAMESPACES distributed slice to registry crate
• Each namespace advertises a name + function source (e.g., kernel registry)
• Provide lookup helpers: namespace_exists(), get_namespace(), list_namespaces()
• No dynamic loading; static link-only

Notes

• This is a foundation for future plugin loader integration
• Keeps compiler namespace-agnostic

Acceptance

• Namespaces register themselves at link time
• Registry exposes namespace metadata with zero compiler hardcoding