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/ReplayReader.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <cstdint>
+#include <memory>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "Tick.h"
+
+struct Command;
+
+struct ReplayHeader
+{
+    int          version = 0;
+    std::string  build;
+    unsigned int seed = 0;
+    std::string  configHash;
+    std::string  timestamp;
+};
+
+// One entry of the replay stream: either a command (applied at its tick) or an
+// RNG checksum (verified at its tick). Entries are kept in file order, which is
+// the canonical order the playback driver reproduces.
+struct ReplayEntry
+{
+    Tick                           tick        = 0;
+    bool                           isCommand   = false;
+    std::shared_ptr<const Command> command;        // set iff isCommand
+    std::uint64_t                  fingerprint = 0; // set iff !isCommand
+};
+
+struct ParsedReplay
+{
+    ReplayHeader             header;
+    std::vector<ReplayEntry> entries;
+};
+
+// Parses a replay file (header + command/checksum stream). Returns nullopt on an
+// I/O failure or malformed content (e.g. an unparseable command line).
+std::optional<ParsedReplay> readReplayFile(const std::string& path);