move FactoryState ownership out of BuildingSystem to Simulation

Simulation (and ArenaSimulation in the balancing tool) now owns the factory's
world data; BuildingSystem holds a reference to it. This is what lets the systems
that operate on the data be handed the same state — phase 3's construction and
deconstruction systems, and later the ecs/system/ classes that today take a
BuildingSystem& only to query it.

reset() clears the state alongside m_admin and m_beltSystem, matching how the
subsystems were already rebuilt from scratch.

Falls short of the tick-argument form I sketched: BuildingSystem still reaches
the data through a member reference rather than a parameter. Making it truly
stateless means the const query surface has to find the data some other way, and
that surface is large — findBuilding alone has 64 call sites, with findSite,
getAllBuildings, getAllSites, isTileOccupied and the rest behind it. Doing that
needs a queries facade behind Simulation::getBuildings() so the callers do not
all move, which is its own decision rather than a side effect of this one.

The constructor gains a parameter, so the four owners and the three test fixtures
that build a BuildingSystem directly are updated; the 33 files that only use one
are untouched.

Verified with a golden-checksum capture before and after — all four sample ticks
identical.

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

src/lib/sim/Simulation.cpp

@@ -94,6 +94,7 @@ void Simulation::reset(unsigned int seed)
     m_pendingSchematicChoices.clear();
 
     m_admin.clear();
+    m_factoryState = FactoryState{};
     m_beltSystem = BeltSystem(m_config.world.beltSpeed_tps);
     initializeSubsystems();
 
@@ -105,6 +106,7 @@ void Simulation::initializeSubsystems()
 {
     m_buildingSystem = std::make_unique<BuildingSystem>(
         m_config,
+        m_factoryState,
         m_beltSystem,
         [this]() { return allocateBuildingId(); },
         [this](int amount) { m_buildingBlocksStock += amount; },