tests: live-HSMS GEM 300 lifecycle scenario via emulator pair

test_gem300_scenario.cpp drives EquipmentDataModel in-memory.  This
companion test does the same lifecycle through actual hsms::Connection
frames on a loopback socket pair:

  S1F13/F14   establish comm
  S3F17/F18   carrier action ProceedWithCarrier (E87)
  S16F11/F12  process job create (E40)
  S14F9/F10   control job create (E94)
  S16F27/F28  CJSTART → CJ → Executing
  S6F11       ControlJobExecuting CEID auto-emitted on transition
  CJ → Completed via internal AllJobsComplete

EquipmentEmulator owns the data model + a passive Connection,
registers state-change handlers that synthesize S6F11/S16F9 on
transitions, and dispatches the inbound primaries above.  HostEmulator
wraps the active Connection and captures everything the equipment
sends unsolicited.

This is the wire-level equivalent of the existing in-memory scenario,
which closes the gap between "FSM works" and "full GEM 300 stack
works on a wire".

Closes #10 in the test-gap backlog.

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

CMakeLists.txt

@@ -128,6 +128,7 @@ add_executable(secsgem_tests
   tests/test_e84.cpp
   tests/test_gem300_scenario.cpp
   tests/test_wire_ceid_emission.cpp
+  tests/test_live_gem300.cpp
 )
 target_link_libraries(secsgem_tests PRIVATE secsgem doctest::doctest)
 target_compile_definitions(secsgem_tests PRIVATE