replay: record every run to a replay file (Phase 2)

Hooks a recorder into the command chokepoint so each run is written to disk as
it plays, ready for playback in Phase 3.

- ReplayRecorder (lib): line-oriented append-friendly file — keyed header
  (version, build, seed, config_hash, timestamp), then '---', then tick-tagged
  command lines interleaved with "# checksum <tick> <hex>" RNG fingerprints.
  Each line is flushed so a crash leaves a valid partial file. Config hash is a
  64-bit FNV over the config dir's *.toml files; build tag is __DATE__/__TIME__.
- CommandSerializer (lib): per-command text (length-prefixed variable parts;
  ship layouts and splitter filters serialized inline). Reset is a file
  boundary, never a stream entry.
- CommandManager owns an optional ReplayRecorder: drain() records each applied
  command + a post-apply checksum; a drained Reset rolls to a new file;
  recordTickCheckpoint() (called per tick from onFrame) writes a checksum every
  30 ticks.
- Random seed generated in main and on restart (std::random_device); Simulation
  retains it via getSeed() for the header.
- GameWorldView attaches the recorder at construction (first file + tick-0
  checksum); replays land in <data>/replays named <timestamp>_<seed>.replay.

ReplayRecorderTest covers serialization, file well-formedness, file rolling,
and the CommandManager drain->record integration. Full suite green
(346 cases / 3377 assertions); app, tests, and balancing all build.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DUsFgd2Ga6pmLz8giS8WUn

src/ui/MainWindow.cpp

@@ -1,6 +1,7 @@
 #include "MainWindow.h"
 
 #include <map>
+#include <random>
 #include <set>
 
 #include <QApplication>
@@ -41,7 +42,7 @@ MainWindow::MainWindow(Simulation* sim, const std::string& configDir, QWidget* p
 
     m_headerBar = new HeaderBar(this);
 
-    m_gameWorldView = new GameWorldView(sim, &sim->config(), &m_visuals, this);
+    m_gameWorldView = new GameWorldView(sim, &sim->config(), &m_visuals, m_configDir, this);
 
     m_sidePanel = new QWidget(this);
     QVBoxLayout* sideLayout = new QVBoxLayout(m_sidePanel);
@@ -184,9 +185,10 @@ void MainWindow::handleEvent(std::shared_ptr<const EscapeMenuRequestedEvent> /*e
             return;
         }
         // Restart is a command boundary; the view resets when the drain applies
-        // it (see GameWorldView::onFrame). Seed stays 0 in Phase 1.
+        // it (see GameWorldView::onFrame). A fresh random seed starts a new run.
         std::shared_ptr<ResetCommand> command = std::make_shared<ResetCommand>();
         command->config = std::move(newConfig);
+        command->seed   = std::random_device{}();
         EventManager::getInstance()->sendEventImmediately(
             std::make_shared<CommandRequestedEvent>(command));
     }
@@ -332,6 +334,7 @@ void MainWindow::handleEvent(std::shared_ptr<const GameOverEvent> /*event*/)
         // Restart is a command boundary; the view resets when the drain applies it.
         std::shared_ptr<ResetCommand> command = std::make_shared<ResetCommand>();
         command->config = std::move(newConfig);
+        command->seed   = std::random_device{}();
         EventManager::getInstance()->sendEventImmediately(
             std::make_shared<CommandRequestedEvent>(command));
     }