The engine argument's description now names every built-in engine with what
it suits, so a model can choose one; omitting it still means Default. The fill
tools resolve an omitted strategy to Fill directly instead of through the
session's whole-job default. Front-end tests cover the MCP and console
defaults and keep the description in step with the registry's built-ins.
Console --engine now names a jobs engine for --autonest (solved once
through NestingEngineRegistry.Create and committed onto the plate) or a
built-in fill strategy for single-plate fill through the public
PlateFillService; unknown names exit with the valid choices instead of
consulting the process-global legacy registry. MCP nesting tools take an
explicit engine argument per call with the session default, never read
process-global active-engine state, and reject whole-job engine names on
single-plate fill tools. NestingEngineRegistry gains an explicit Create
(name) resolution; PlateFillService gains a public ResolveStrategy and a
plate-number Nest overload used by interactive callers.
aj
