refactor: migrate to multi-project structure

マルチプロジェクト構造に移行し，Paper と Velocity の両方をサポートできるようにしました．

- engine: 共通ロジック（データモデル，JSON シリアライゼーション）
- platform-paper: Paper プラグイン実装
- platform-velocity: Velocity プラグイン実装（将来用）

主な変更:
- settings.gradle.kts: サブプロジェクト定義を追加
- build.gradle.kts: マルチプロジェクト用に再構成
- 既存コードを platform-paper に移動
- CI/CD ワークフローを更新
- Docker 設定を更新
- IntelliJ Run Configurations を更新

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 21 insertions, 36 deletions

diff --git a/build.gradle.kts b/build.gradle.kts
index 7546945..488ce4e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,46 +1,31 @@
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
 plugins {
-    kotlin("jvm") version "2.3.0"
-    id("com.gradleup.shadow") version "8.3.0"
-    id("xyz.jpenilla.run-paper") version "2.3.1"
-    id("org.jlleitschuh.gradle.ktlint") version "14.0.1"
-    id("org.jetbrains.dokka") version "2.1.0"
+    kotlin("jvm") version "2.3.0" apply false
+    kotlin("plugin.serialization") version "2.3.0" apply false
+    id("com.gradleup.shadow") version "8.3.0" apply false
+    id("xyz.jpenilla.run-paper") version "2.3.1" apply false
+    id("org.jlleitschuh.gradle.ktlint") version "14.0.1" apply false
+    id("org.jetbrains.dokka") version "2.1.0" apply false
 }
 
-group = "dev.m1sk9"
-version = "0.0.0"
+allprojects {
+    group = "dev.m1sk9"
+    version = "0.0.0"
 
-repositories {
-    mavenCentral()
-    maven("https://repo.papermc.io/repository/maven-public/") {
-        name = "papermc-repo"
+    repositories {
+        mavenCentral()
     }
 }
 
-dependencies {
-    compileOnly("io.papermc.paper:paper-api:1.21.11-R0.1-SNAPSHOT")
-    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
-}
-
-tasks {
-    runServer {
-        minecraftVersion("1.21")
-    }
-}
-
-val targetJavaVersion = 21
-kotlin {
-    jvmToolchain(targetJavaVersion)
-}
-
-tasks.build {
-    dependsOn("shadowJar")
-}
+subprojects {
+    apply(plugin = "org.jetbrains.kotlin.jvm")
+    apply(plugin = "org.jlleitschuh.gradle.ktlint")
 
-tasks.processResources {
-    val props = mapOf("version" to version)
-    inputs.properties(props)
-    filteringCharset = "UTF-8"
-    filesMatching("paper-plugin.yml") {
-        expand(props)
+    tasks.withType<KotlinCompile> {
+        compilerOptions {
+            jvmTarget.set(JvmTarget.JVM_21)
+        }
     }
 }