Add std namespace registration and docs examples

[ztripez]

Goal

Introduce a std namespace registered via the new namespace registry, and update docs/examples to demonstrate std.* vs kernel.* usage.

Scope

• Create a std namespace descriptor (even if it aliases existing kernel functions)
• Document namespace semantics in DSL docs
• Add example usage showing std.* and kernel.* coexistence

Acceptance

• std namespace appears in registry listings
• Docs updated to reference namespace-based calls