Compiler resolves namespaced calls via registry

[ztripez]

Goal

Make the compiler resolve namespace.func(...) by consulting the namespace registry rather than hardcoding kernel or std.

Scope

• Update parsing/lowering to recognize any registered namespace
• Update validation to check functions against the resolved namespace
• Extend IR call representation to include namespace (or equivalent metadata)
• Preserve existing behavior for kernel.* calls

Acceptance

• Calls like kernel.integrate resolve via registry
• Unknown namespaces/functions yield clear diagnostics
• Compiler contains no hardcoded list of namespaces