feat: personal run replays (ghost system)

- GhostData: worldName field, format v4; GhostManager stores last N runs per player (ghosts/<uuid>/<ts>.ghost)
- GhostService: per-player recording (start on run start, every tick, finalize on fall), gated by ghost-mode.enabled + per-player toggle
- PlayerGhost: packet-based fake-player NPC with viewer skin (NMS via remapNms gradle task, reflection send, graceful degradation)
- GhostReplay: teleport viewer to run start, replay frames via PlayerGhost, restore on finish
- /lp replay [index] command + tab completion; settings menu ghost_recording toggle (persisted disk/SQL)
- config: ghost-mode.{enabled,max-runs}, remove dead show-top/transparency + GHOST_* statics
- tests: GhostData v4 round-trip, GhostManager eviction/ordering, yawToFixed (79 total)

src/test/java/dev/loki/loparkour/ghost/GhostManagerTest.java

@@ -0,0 +1,114 @@
+package dev.loki.loparkour.ghost;
+
+import dev.loki.loparkour.ghost.core.GhostManager;
+import dev.loki.loparkour.ghost.model.GhostData;
+import dev.loki.loparkour.ghost.model.GhostFrame;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.DataOutputStream;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Unit tests for the per-player personal replay storage of {@link GhostManager}.
+ */
+class GhostManagerTest {
+
+    private static final int EVICTION_CAP = 2;
+
+    /**
+     * A manager whose run cap is fixed, overriding the config-driven {@link #maxRuns()}.
+     * Chosen over mutating {@code Config} statics, which the plugin initializes at
+     * enable time and are not settable from unit tests.
+     */
+    private static final class FixedCapManager extends GhostManager {
+
+        private FixedCapManager(File ghostFolder) {
+            super(ghostFolder);
+        }
+
+        @Override
+        public int maxRuns() {
+            return EVICTION_CAP;
+        }
+    }
+
+    private static GhostData run(UUID uuid, String name, int score, long timestamp) {
+        final List<GhostFrame> frames = new ArrayList<>();
+        frames.add(new GhostFrame(0, 0, 100, 0, 0, 0));
+        return new GhostData(uuid, name, score, timestamp, "world", frames);
+    }
+
+    @Test
+    void saveRunAndGetRunsReturnNewestFirst(@TempDir Path tempDir) throws IOException {
+        final UUID uuid = UUID.randomUUID();
+        final GhostManager manager = new GhostManager(tempDir.toFile());
+        final long base = 1_700_000_000_000L;
+
+        manager.saveRun(uuid, run(uuid, "A", 10, base));
+        manager.saveRun(uuid, run(uuid, "B", 20, base + 1_000));
+        manager.saveRun(uuid, run(uuid, "C", 30, base + 2_000));
+
+        final List<GhostData> runs = manager.getRuns(uuid);
+
+        assertEquals(3, runs.size());
+        assertEquals(base + 2_000, runs.get(0).getTimestamp());
+        assertEquals(30, runs.get(0).getScore());
+        assertEquals(base, runs.get(2).getTimestamp());
+        assertEquals(10, runs.get(2).getScore());
+    }
+
+    @Test
+    void saveRunEvictsOldestBeyondCap(@TempDir Path tempDir) throws IOException {
+        final UUID uuid = UUID.randomUUID();
+        final GhostManager manager = new FixedCapManager(tempDir.toFile());
+        final long base = 1_700_000_000_000L;
+
+        for (int i = 0; i < 5; i++) {
+            manager.saveRun(uuid, run(uuid, "P" + i, i * 10, base + i * 1_000L));
+        }
+
+        final List<GhostData> runs = manager.getRuns(uuid);
+
+        assertEquals(EVICTION_CAP, runs.size(), "Old runs beyond the cap must be evicted");
+        assertEquals(base + 4_000, runs.get(0).getTimestamp());
+        assertEquals(base + 3_000, runs.get(1).getTimestamp());
+    }
+
+    @Test
+    void getRunsWithEmptyFolderReturnsEmptyList(@TempDir Path tempDir) {
+        final GhostManager manager = new GhostManager(tempDir.toFile());
+
+        final List<GhostData> runs = manager.getRuns(UUID.randomUUID());
+
+        assertTrue(runs.isEmpty(), "Player with no saved runs should return an empty list");
+    }
+
+    @Test
+    void getRunsIgnoresStaleFormatFiles(@TempDir Path tempDir) throws IOException {
+        final UUID uuid = UUID.randomUUID();
+        final GhostManager manager = new GhostManager(tempDir.toFile());
+        manager.saveRun(uuid, run(uuid, "New", 10, 1_700_000_000_000L));
+
+        // Corrupt one file so it reads as an unsupported version
+        final File playerFolder = new File(tempDir.toFile(), uuid.toString());
+        final File[] files = playerFolder.listFiles((dir, name) -> name.endsWith(".ghost"));
+        assertNotNull(files);
+        try (DataOutputStream out = new DataOutputStream(
+                new FileOutputStream(files[0], false))) {
+            out.writeInt(2);
+        }
+
+        final List<GhostData> runs = manager.getRuns(uuid);
+
+        assertTrue(runs.isEmpty(), "Stale-format files must be skipped and deleted");
+    }
+}