refactor(player): encapsulate game state behind PlayerSettings, clear VisibilityModifier and HiddenField

- ParkourUser/ParkourPlayer/GeneratorState public mutable fields -> private + short accessors
- per-player settings extracted to player/data/PlayerSettings (ParkourPlayer 188 -> 96 lines,
  PMD-counted methods 20 -> 9); this is what fixed the TooManyMethods violation that the
  encapsulation itself introduced — by decomposition, not by lowering the threshold
- disk storage reads and writes the same canonical 12-key map as the SQL JSON column;
  legacy key names normalized on read, @Expose dropped from domain classes
- 39 settings call sites rewritten across 7 files
- HiddenField backlog cleared (Config, ObstacleGenerator, GhostService, Leaderboard,
  PagedMenu, Reward, ParticleData, World)
- checkstyle ratchet: VisibilityModifier, HiddenField, EmptyLineSeparator and
  MissingDeprecated flipped to error once their counters hit zero; suppressions.xml empty
- javac -Xmaxwarns raised so NullAway/Error Prone counts are honest
  (baseline 165/289, now 164/265)

checkstyle 0 errors / 135 warnings, PMD 0 violations, tests 94/0 fail, ./gradlew check green.
TODO.md: items 30 and 107 updated, new items 167-170, ПРОГРЕСС-6/7 recorded.

src/main/java/dev/loki/loparkour/schematic/config/SchematicDifficultyConfig.java

@@ -5,6 +5,7 @@ import dev.loki.loparkour.schematic.core.SchematicManager;
 import org.bukkit.configuration.file.YamlConfiguration;
 import org.jetbrains.annotations.NotNull;
 
+import java.io.File;
 import java.io.IOException;
 
 /**
@@ -16,16 +17,16 @@ public final class SchematicDifficultyConfig {
     }
 
     public static void setDifficulty(@NotNull String fileStem, double difficulty) throws IOException {
-        if (Config.SCHEMATICS.path == null) {
+        final File configFile = Config.SCHEMATICS.path();
+        if (configFile == null) {
             throw new IOException("Schematics config path is not initialized");
         }
 
-        final YamlConfiguration yaml = YamlConfiguration.loadConfiguration(Config.SCHEMATICS.path);
+        final YamlConfiguration yaml = YamlConfiguration.loadConfiguration(configFile);
         final String key = SchematicManager.configKey(fileStem);
         yaml.set("difficulty." + key, difficulty);
-        yaml.save(Config.SCHEMATICS.path);
+        yaml.save(configFile);
 
-        Config.SCHEMATICS.fileConfiguration = YamlConfiguration.loadConfiguration(Config.SCHEMATICS.path);
         Config.SCHEMATICS.load();
     }
 }