H1: ModuleStateMachine + ModuleStore (E157 §6)

Per-module process-tracking state machine.  An E157 instance models a
single recipe step at a single module, with the canonical lifecycle:

  NotExecuting -> GeneralExecuting (StartGeneral)
                -> StepExecuting   (StartStep)
                -> StepCompleted   (CompleteStep)

Plus universal escape hatches: Reset returns any state to
NotExecuting; Abort terminates from any state to StepCompleted.

ModuleStore wraps the FSM with the now-standard pattern:
  - non-movable (this-capture lambdas)
  - per-module bind() carries current_substid + recipe_step
  - fire(module_id, event) delegates to the FSM
  - set_state_change_handler observes every transition with module_id

Joins EquipmentDataModel.  5 test cases cover happy path, Reset from
each interior state, Abort, store-level create dedup + bind, and the
multi-module change handler keying.

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

include/secsgem/gem/data_model.hpp

@@ -11,6 +11,7 @@
 #include "secsgem/gem/store/exceptions.hpp"
 #include "secsgem/gem/store/host_commands.hpp"
 #include "secsgem/gem/store/limits.hpp"
+#include "secsgem/gem/store/modules.hpp"
 #include "secsgem/gem/store/process_jobs.hpp"
 #include "secsgem/gem/store/substrates.hpp"
 #include "secsgem/gem/store/recipes.hpp"
@@ -45,6 +46,7 @@ struct EquipmentDataModel {
   SubstrateStore            substrates;
   EptStateMachine           ept;
   CemObjectStore            cem;
+  ModuleStore               modules;
 
   // Convenience: VID -> value lookup spanning SVIDs and DVIDs.
   std::optional<s2::Item> vid_value(uint32_t vid) const {