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)

build.gradle.kts

@@ -1,3 +1,19 @@
+import java.io.File
+import java.net.URI
+import java.util.zip.ZipFile
+
+// Remap tooling: rebuilds the Mojang-mapped 1.20.4 NMS classes at build time.
+buildscript {
+    repositories {
+        mavenCentral()
+        maven("https://maven.fabricmc.net/")
+    }
+    dependencies {
+        classpath("net.fabricmc:mapping-io:0.6.1")
+        classpath("net.fabricmc:tiny-remapper:0.9.0")
+    }
+}
+
 plugins {
     id("java")
     id("io.github.goooler.shadow") version("8.1.8")
@@ -77,6 +93,63 @@ repositories {
     }
 }
 
+// --- Mojang-mapped NMS (net.minecraft.*) for the packet NPC renderer ---------
+// repo.papermc.io purged the old io.papermc.paper:paper:1.20.4-R0.1-SNAPSHOT
+// dev-bundle, so the 1.20.4 vanilla server jar (bundler/obfuscated) is remapped
+// with Mojang's official mappings via tiny-remapper into the same Mojang-mapped
+// classes the dev-bundle shipped. Result is cached under the Gradle user home.
+val nmsVersion = "1.20.4"
+val nmsCacheDir = gradle.gradleUserHomeDir.resolve("caches/loparkour-nms/$nmsVersion")
+val nmsServerJar = nmsCacheDir.resolve("server.jar")
+val nmsNestedJar = nmsCacheDir.resolve("server-nested.jar")
+val nmsMappings = nmsCacheDir.resolve("server-mappings.txt")
+val nmsTiny = nmsCacheDir.resolve("server-mappings.tiny")
+val nmsMappedJar = nmsCacheDir.resolve("server-mojang-mapped.jar")
+val nmsAuthlibJar = nmsCacheDir.resolve("authlib-6.0.52.jar")
+
+val remapNms by tasks.registering {
+    outputs.files(nmsServerJar, nmsMappings, nmsMappedJar, nmsAuthlibJar)
+    doLast {
+        nmsCacheDir.mkdirs()
+        fun download(url: String, target: File) {
+            if (target.isFile) {
+                return
+            }
+            URI(url).toURL().openStream().use { input ->
+                target.outputStream().use { input.copyTo(it) }
+            }
+        }
+        download("https://piston-data.mojang.com/v1/objects/8dd1a28015f51b1803213892b50b7b4fc76e594d/server.jar", nmsServerJar)
+        download("https://piston-data.mojang.com/v1/objects/c1cafe916dd8b58ed1fe0564fc8f786885224e62/server.txt", nmsMappings)
+        download("https://libraries.minecraft.net/com/mojang/authlib/6.0.52/authlib-6.0.52.jar", nmsAuthlibJar)
+        if (!nmsNestedJar.isFile) {
+            ZipFile(nmsServerJar).use { zip ->
+                zip.getInputStream(zip.getEntry("META-INF/versions/$nmsVersion/server-$nmsVersion.jar")).use { input ->
+                    nmsNestedJar.outputStream().use { input.copyTo(it) }
+                }
+            }
+        }
+        val tree = net.fabricmc.mappingio.tree.MemoryMappingTree(false)
+        net.fabricmc.mappingio.MappingReader.read(nmsMappings.toPath(), net.fabricmc.mappingio.format.MappingFormat.PROGUARD_FILE, tree)
+        net.fabricmc.mappingio.MappingWriter.create(nmsTiny.toPath(), net.fabricmc.mappingio.format.MappingFormat.TINY_2_FILE).use { writer ->
+            tree.accept(net.fabricmc.mappingio.adapter.MappingSourceNsSwitch(writer, "target"))
+        }
+        val remapper = net.fabricmc.tinyremapper.TinyRemapper.newRemapper()
+            .withMappings(net.fabricmc.tinyremapper.TinyUtils.createTinyMappingProvider(nmsTiny.toPath(), "target", "source"))
+            .ignoreConflicts(true)
+            .rebuildSourceFilenames(true)
+            .build()
+        net.fabricmc.tinyremapper.OutputConsumerPath.Builder(nmsMappedJar.toPath()).build().use { output ->
+            output.addNonClassFiles(nmsNestedJar.toPath())
+            remapper.readInputs(nmsNestedJar.toPath())
+            remapper.apply(output)
+        }
+        remapper.finish()
+    }
+}
+
+tasks.withType<JavaCompile>().configureEach { dependsOn(remapNms) }
+
 // Resolve the org.bukkit:bukkit capability conflict that newer paper-api artifacts
 // introduce (they both bundle the bukkit classes and declare the capability).
 configurations.configureEach {
@@ -100,6 +173,13 @@ dependencies {
     } else {
         compileOnly(apiCoordinate)
     }
+
+    // NMS (net.minecraft.*) for packet NPC rendering — compileOnly, Mojang-mapped.
+    // Built once by the remapNms task above (vanilla 1.20.4 server + official
+    // mappings) because the io.papermc.paper:paper:1.20.4 dev-bundle was purged.
+    compileOnly(files(nmsMappedJar, nmsAuthlibJar))
+    // fastutil types are referenced by the NMS packet signatures (IntList).
+    compileOnly("it.unimi.dsi:fastutil:8.5.9")
     
     // Adventure API (for Component)
     compileOnly("net.kyori:adventure-api:4.14.0")
@@ -133,6 +213,8 @@ dependencies {
     testImplementation("org.mockito:mockito-junit-jupiter:5.10.0")
     testImplementation("org.spigotmc:spigot-api:1.20.4-R0.1-SNAPSHOT")
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+    // Test runtime classpath for loading PlayerGhost (references NMS + authlib types).
+    testImplementation(files(nmsMappedJar, nmsAuthlibJar))
 }
 
 tasks.shadowJar {