Replay: deterministic record & playback (#4)

Add deterministic record/playback for a run.

Recording captures `(seed, config hash, ordered tick-tagged commands)` and re-simulates on playback — no state snapshots. `DotaFactory.exe --replay <file>` re-plays a recorded run view-only with manual speed/pause.

Reviewed-on: #4
Co-authored-by: Malte Langkabel <malte.langkabel@gmail.com>
Co-committed-by: Malte Langkabel <malte.langkabel@gmail.com>

src/test/SimulationTestAccess.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <QPoint>
+
+#include "BuildingId.h"
+#include "BuildingType.h"
+#include "Rotation.h"
+#include "Simulation.h"
+
+class BeltSystem;
+class BuildingSystem;
+
+// Test-only backdoor to Simulation's private player-action mutators and mutable
+// subsystem accessors. Declared a friend of Simulation, so it can hand tests the
+// same mutation surface that Simulation::apply uses internally — without exposing
+// those mutators to production (UI/app) code, which must go through the command
+// chokepoint (docs/replay_design.md).
+//
+// This header lives under src/test and is not on the lib/ui/app include path, so
+// only test translation units can reach it. Non-player test setup that has no
+// command equivalent (e.g. placeImmediate, forEachBuilding buffer injection) is
+// reached via buildings(sim)/belts(sim).
+struct SimulationTestAccess
+{
+    static BuildingSystem& buildings(Simulation& sim) { return sim.buildingsMutable(); }
+    static BeltSystem&     belts(Simulation& sim)     { return sim.beltsMutable(); }
+
+    static BuildingId place(Simulation& sim, BuildingType type, QPoint anchor,
+                            Rotation rotation)
+    {
+        return sim.tryPlaceBuilding(type, anchor, rotation);
+    }
+
+    static void demolish(Simulation& sim, BuildingId id) { sim.demolish(id); }
+
+    static void applySchematicChoice(Simulation& sim, int choiceIndex)
+    {
+        sim.applySchematicChoice(choiceIndex);
+    }
+};