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/lib/sim/ReplayPlayer.cpp

@@ -0,0 +1,56 @@
+#include "ReplayPlayer.h"
+
+#include <utility>
+
+#include "Command.h"
+#include "Simulation.h"
+
+ReplayPlayer::ReplayPlayer(Simulation& simulation, std::vector<ReplayEntry> entries)
+    : m_simulation(simulation)
+    , m_entries(std::move(entries))
+{
+}
+
+void ReplayPlayer::start()
+{
+    processEntriesAt(0);
+}
+
+void ReplayPlayer::advanceTo(Tick tick)
+{
+    processEntriesAt(tick);
+}
+
+bool ReplayPlayer::isFinished() const
+{
+    return m_desyncTick.has_value() || m_cursor >= m_entries.size();
+}
+
+std::optional<Tick> ReplayPlayer::getDesyncTick() const
+{
+    return m_desyncTick;
+}
+
+void ReplayPlayer::processEntriesAt(Tick tick)
+{
+    // Consume entries for this tick in file order. The recording writes, at a
+    // given tick: the periodic checksum (if any) first, then command lines each
+    // followed by their post-apply checksum — so applying/verifying in file order
+    // reproduces the original sequence exactly.
+    while (!m_desyncTick.has_value()
+           && m_cursor < m_entries.size()
+           && m_entries[m_cursor].tick == tick)
+    {
+        const ReplayEntry& entry = m_entries[m_cursor];
+        ++m_cursor;
+
+        if (entry.isCommand)
+        {
+            m_simulation.apply(*entry.command);
+        }
+        else if (m_simulation.rngFingerprint() != entry.fingerprint)
+        {
+            m_desyncTick = tick;
+        }
+    }
+}