implement artifact win condition (REQ-WIN-ARTIFACT-COUNT, REQ-WIN-SCREEN)

- Add [artifacts] config section to world.toml with artifact_chance_formula (x = station level) and artifact_win_count
- Roll artifact chance before each schematic drop; on success show 2 schematics + Artifact option instead of 3
- Selecting Artifact increments artifact count; reaching artifact_win_count triggers win screen
- Display "Artifacts: x/y" in header bar via ArtifactCountChangedEvent
- Win screen mirrors game-over screen with "Won!" caption and same Restart/Quit buttons

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DUsFgd2Ga6pmLz8giS8WUn

src/lib/config/ConfigLoader.cpp

@@ -301,6 +301,9 @@ WorldConfig ConfigLoader::loadWorld(const std::string& path)
     cfg.targeting.overclaimPenaltyFormula = requireFormula(tbl["targeting"]["overclaim_penalty_formula"], file, "targeting.overclaim_penalty_formula");
     cfg.targeting.hysteresis              = requireDouble(tbl["targeting"]["target_hysteresis"],          file, "targeting.target_hysteresis");
 
+    cfg.artifacts.artifactChanceFormula = requireFormula(tbl["artifacts"]["artifact_chance_formula"], file, "artifacts.artifact_chance_formula");
+    cfg.artifacts.artifactWinCount      = static_cast<int>(requireInt(tbl["artifacts"]["artifact_win_count"], file, "artifacts.artifact_win_count"));
+
     return cfg;
 }
 

src/lib/config/WorldConfig.h

@@ -47,6 +47,13 @@ struct WorldTargeting
     double  hysteresis;               // fractional margin a challenger must beat the current target by
 };
 
+// Artifact win condition (REQ-WIN-ARTIFACT-COUNT, REQ-WIN-SCREEN).
+struct WorldArtifacts
+{
+    Formula artifactChanceFormula;  // x = station level, result clamped to [0,1]
+    int     artifactWinCount;
+};
+
 struct WorldConfig
 {
     int heightTiles;                    // REQ-GW-HEIGHT
@@ -65,4 +72,5 @@ struct WorldConfig
     WorldPush push;
     WorldWaves waves;
     WorldTargeting targeting;
+    WorldArtifacts artifacts;
 };