refactor: decompose god-classes, add lint gates, restructure packages

- Decompose all 11 god-classes (>200 lines) into facade + collaborators
  (command/, schematic/, config/, generator/, mode/, papi/, adaptive/,
  storage/, player/, leaderboard/) — every file is now <=200 lines
- Add PMD 7 (report-only) + stricter checkstyle rules (NPath, IllegalCatch,
  NestedDepth, Whitespace, MissingOverride); fix real bugs found
  (printStackTrace, resource leaks in ConfigLoader/SQLStatsStorage)
- docs/ARCHITECTURE.md: target structure + 'one folder = one purpose' rule
- Pilot restructure: command/core|util/, mode/impl/solo|multi|barrier/,
  hook/papi/resolver/; cross-package classes made public
- TODO.md: track warning cleanup (132-138) + restructure progress

src/main/java/dev/loki/loparkour/LoParkour.java

@@ -18,6 +18,7 @@ import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.util.ArrayList;
+import java.util.logging.Level;
 
 /**
  * Main class of LoParkour
@@ -112,8 +113,7 @@ public final class LoParkour extends LoPlugin {
             Storage.close();
             World.delete();
         } catch (Throwable t) {
-            getLogger().severe("Error during plugin shutdown: " + t.getMessage());
-            t.printStackTrace();
+            getLogger().log(Level.SEVERE, "Error during plugin shutdown: " + t.getMessage(), t);
         }
     }
 }