boundary.sx now contains only generic web-platform I/O primitives that
any SX host would provide (current-user, request-arg, url-for, etc.).
Moved to boundary-app.sx (deployment-specific):
- Inter-service: frag, query, action, service
- Framework: htmx-request?, g, jinja-global
- Domain: nav-tree, get-children, relations-from
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>