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/BuildingSystem.h

@@ -47,6 +47,7 @@ class BuildingSystem
 {
 public:
     BuildingSystem(const GameConfig& config,
+                   FactoryState& state,
                    BeltSystem& belts,
                    std::function<BuildingId()> allocateBuildingId,
                    std::function<void(int)> addBuildingBlocks,
@@ -285,6 +286,11 @@ private:
                             QPoint anchor) const;
 
     const GameConfig&                              m_config;
+
+    // The factory's world data — buildings, queued work, tile ownership. Owned by
+    // Simulation, not by this system (see FactoryState.h).
+    FactoryState&                                  m_state;
+
     BeltSystem&                                    m_belts;
     std::function<BuildingId()>                      m_allocateBuildingId;
     std::function<void(int)>                       m_addBuildingBlocks;
@@ -293,9 +299,4 @@ private:
     std::function<bool(const std::string&)>        m_isItemUnlocked;
     std::mt19937&                                  m_rng;
     int                                            m_asteroidWidth_tiles;
-
-    // The factory's world data — buildings, queued work, tile ownership. Held here
-    // for now; the intent is for Simulation to own it and pass it into the tick
-    // methods, leaving this system stateless over it (see FactoryState.h).
-    FactoryState m_state;
 };