refactor: split 6 oversized packages into semantic subpackages

Structure debt list is now empty (FOLDER_DEBT = Set.of()), every folder
holds at most 4 java files:

- elytra/{mode,generator} -> elytra/core plus per-mode slices (close,
  minspeed, obstacle, speeddemon, timetrial), 2 files each
- command/schematic -> command/schematic (4) + wand/ (2)
- generator/jump: JumpType -> jump/model/, SchematicBlockPlacer ->
  jump/placement/schematic/
- player/core -> player/core (4) + PlayerSpawnSetup -> player/service (4)

18 files moved, imports/tests updated, 5 classes widened to public for
cross-package calls. No behavior change; check and build stay green.

src/main/java/dev/loki/loparkour/elytra/mode/ObstacleMode.java

@@ -1,55 +0,0 @@
-package dev.loki.loparkour.elytra.mode;
-
-import dev.loki.loparkour.config.locale.Locales;
-import dev.loki.loparkour.elytra.generator.ObstacleGenerator;
-import dev.loki.loparkour.leaderboard.core.Leaderboard;
-import dev.loki.loparkour.mode.base.Mode;
-import dev.loki.loparkour.mode.base.ModeMessages;
-import dev.loki.loparkour.player.core.ParkourPlayer;
-import dev.loki.loparkour.session.core.Session;
-import dev.loki.loparkour.util.item.Item;
-import org.bukkit.entity.Player;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-
-/**
- * Elytra mode with client-side obstacles to fly around.
- */
-public class ObstacleMode implements Mode {
-
-    private final Leaderboard leaderboard = new Leaderboard(getName(), Leaderboard.Sort.SCORE);
-
-    @Override
-    @NotNull
-    public String getName() {
-        return "obstacle";
-    }
-
-    @Override
-    @Nullable
-    public Item getItem(String locale) {
-        return Locales.getItem(locale, "play.elytra.obstacle");
-    }
-
-    @Override
-    @NotNull
-    public Leaderboard getLeaderboard() {
-        return leaderboard;
-    }
-
-    @Override
-    public void create(Player player) {
-        if (!ModeMessages.checkJoiningEnabled(player)) {
-            return;
-        }
-
-        final ParkourPlayer pp = ParkourPlayer.getPlayer(player);
-        if (pp != null && pp.session.generator != null && pp.session.generator.getMode() instanceof ObstacleMode) {
-            return;
-        }
-
-        player.closeInventory();
-
-        Session.create(ObstacleGenerator::new, null, null, player);
-    }
-}