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.cpp

@@ -0,0 +1,145 @@
+#include "ReplayReader.h"
+
+#include <fstream>
+#include <sstream>
+#include <string>
+
+#include "Command.h"
+#include "CommandSerializer.h"
+
+namespace
+{
+void stripCarriageReturn(std::string& line)
+{
+    if (!line.empty() && line.back() == '\r')
+    {
+        line.pop_back();
+    }
+}
+
+// Splits "key value with spaces" into (key, remainder). Remainder may be empty.
+void splitKeyValue(const std::string& line, std::string& key, std::string& value)
+{
+    const std::string::size_type space = line.find(' ');
+    if (space == std::string::npos)
+    {
+        key   = line;
+        value.clear();
+    }
+    else
+    {
+        key   = line.substr(0, space);
+        value = line.substr(space + 1);
+    }
+}
+}  // namespace
+
+std::optional<ParsedReplay> readReplayFile(const std::string& path)
+{
+    std::ifstream stream(path, std::ios::in);
+    if (!stream.is_open())
+    {
+        return std::nullopt;
+    }
+
+    ParsedReplay replay;
+    std::string  line;
+
+    // --- Header (up to the "---" separator) ---
+    bool sawSeparator = false;
+    while (std::getline(stream, line))
+    {
+        stripCarriageReturn(line);
+        if (line == "---")
+        {
+            sawSeparator = true;
+            break;
+        }
+        if (line.empty() || line[0] == '#')
+        {
+            continue;  // banner / blank
+        }
+
+        std::string key;
+        std::string value;
+        splitKeyValue(line, key, value);
+        try
+        {
+            if (key == "version")          { replay.header.version    = std::stoi(value); }
+            else if (key == "build")       { replay.header.build      = value; }
+            else if (key == "seed")        { replay.header.seed       = static_cast<unsigned int>(std::stoul(value)); }
+            else if (key == "config_hash") { replay.header.configHash = value; }
+            else if (key == "timestamp")   { replay.header.timestamp  = value; }
+        }
+        catch (const std::exception&)
+        {
+            return std::nullopt;
+        }
+    }
+
+    if (!sawSeparator)
+    {
+        return std::nullopt;
+    }
+
+    // --- Command / checksum stream ---
+    while (std::getline(stream, line))
+    {
+        stripCarriageReturn(line);
+        if (line.empty())
+        {
+            continue;
+        }
+
+        if (line[0] == '#')
+        {
+            // "# checksum <tick> <hex>"
+            std::istringstream in(line);
+            std::string hash;
+            std::string keyword;
+            ReplayEntry entry;
+            in >> hash >> keyword >> entry.tick >> hash;
+            if (keyword != "checksum")
+            {
+                continue;  // unknown comment line — ignore
+            }
+            try
+            {
+                entry.fingerprint = std::stoull(hash, nullptr, 16);
+            }
+            catch (const std::exception&)
+            {
+                return std::nullopt;
+            }
+            entry.isCommand = false;
+            replay.entries.push_back(std::move(entry));
+            continue;
+        }
+
+        // "<tick> <serialized command>"
+        const std::string::size_type space = line.find(' ');
+        if (space == std::string::npos)
+        {
+            return std::nullopt;
+        }
+        ReplayEntry entry;
+        try
+        {
+            entry.tick = std::stoll(line.substr(0, space));
+        }
+        catch (const std::exception&)
+        {
+            return std::nullopt;
+        }
+        std::shared_ptr<Command> command = parseCommand(line.substr(space + 1));
+        if (!command)
+        {
+            return std::nullopt;
+        }
+        entry.isCommand = true;
+        entry.command   = std::move(command);
+        replay.entries.push_back(std::move(entry));
+    }
+
+    return replay;
+}