BB1: full E40 S16F11 body — MF, PRRECIPEMETHOD, RCPVARS, PRPROCESSPARAMS

Replaces the simplified <L,3 PRJOBID PPID MTRLOUTSPEC> demo body with
the full SEMI E40-0705 §10.2 shape:

  <L,5 PRJOBID MF PRRECIPEMETHOD
       <L,2 PPID <L,n <L,2 RCPPARNM RCPPARVAL>>>
       <L,n MTRLOUTSPEC>
       <L,n <L,2 PARAMNAME PARAMVAL>>>

ProcessJob now carries the extra fields (MaterialFlag, ProcessRecipeMethod,
RcpVar[], ProcessParam[]) so a tool's recipe engine can later consume
the recipe-variable overrides and per-job process parameters.  Server
S16F11 dispatch populates them via the new ProcessJobStore::set_e40_extras
helper after a successful create.

MaterialFlag + ProcessRecipeMethod enums live in their own tiny header
(`e40_constants.hpp`) so process_jobs.hpp (the store) can use them
without dragging in messages_helpers.hpp (which would create a circular
include via data_model.hpp).

The simplified 3-arg HostHandler::send_create_process_job convenience
remains; it constructs a sensible-default PRJobCreateRequest internally.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

include/secsgem/gem/messages_helpers.hpp

@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "secsgem/gem/data_model.hpp"
+#include "secsgem/gem/e40_constants.hpp"
 #include "secsgem/secs2/item.hpp"
 #include "secsgem/secs2/message.hpp"