Every served entrypoint is started as a process speaking MCP over stdio, told its module and node;
one that is not executable is refused by name. The import path, the SDK resolve hook (issue 209)
and the per-registration hand-off go. The one-module form the per-module containers use is still
imported until they move (to-be 38 WP4c). A child's mesh/publish is published as its module and
answered once accepted; a child that dies says why in its own last words. Fixtures are served
through launchers exactly as the builder writes them.
