add UnlockState class for schematic/unlock bookkeeping

Simulation.h/.cpp had grown a large block of schematic/unlock state
(containers, the implicit-unlock traversal, checksum folding) that has
nothing to do with tick orchestration. Split it into its own class so
Simulation stays legible as "tick orchestration + subsystem handles".

This commit only adds the new UnlockState.h/.cpp (registered in
CMakeLists.txt) with the containers, types, and logic moved in
verbatim; nothing references it yet, so this is a no-op for behavior.
Simulation is wired to use it in the next commit.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/lib/sim/CMakeLists.txt

@@ -19,6 +19,7 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipStatsCalculator.h
     ${CMAKE_CURRENT_SOURCE_DIR}/StateChecksum.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ThreatCostCalculator.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/UnlockState.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WaveSystem.h
     PARENT_SCOPE
 )
@@ -40,6 +41,7 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipStatsCalculator.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/StateChecksum.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ThreatCostCalculator.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/UnlockState.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/WaveSystem.cpp
     PARENT_SCOPE
 )