Implements namespace eval, current, which, exists, delete, export,
import, forget, path, and ensemble create (auto-map + -map). Procs
defined inside namespace eval are stored as fully-qualified names
(::ns::proc), resolved relative to the calling namespace at lookup
time. Proc bodies execute in their defining namespace so sibling
calls work without qualification.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
