feat(phase-3): runtime integration — chain damage application + cooldown

Wires the pure ChainResolver (Phase 2) to the live Hytale runtime via
four sceptre/ adapters:
- HytaleEntityAdapter — eager snapshot Ref<EntityStore> -> ChainEntity
  via TransformComponent.getPosition() and EntityStatMap.get(health) > 0
- HytalePlayerRayCaster — captures playerRef, delegates to
  TargetUtil.getTargetEntity (auto eye-origin + head-rotation)
- HytaleEntitySource — wraps TargetUtil.getAllEntitiesInSphere
- ChainDamageApplier — fires DamageSystems.executeDamage per hit;
  injectable DamageExecutor SAM keeps the helper unit-testable.

ChainLightningSceptreInteraction.firstRun is rewritten end-to-end:
cooldown gate (hasCooldown(false) -> deductCharge() only on success),
ray-cast -> BFS -> damage application, structured logging, try/catch
wrapper to keep a runtime fault from killing the server tick.

API corrections discovered against the decompiled jar:
- Ref has no uuid() — use "ref:" + getIndex() for the chain id
- DamageCause.PHYSICAL is @Nullable until runtime — use the int-index
  overload of Damage with index 0
- Static mock of DamageSystems crashes class init — abstracted behind
  a DamageExecutor SAM with a default lazy holder

Tests: 33/33 green (25 from Phase 2 + 4 ChainDamageApplier tests +
4 fixture sanity). ./gradlew build SUCCESSFUL, JAR auto-deployed.
MANUAL UAT (10 items) pending in-game.

build.gradle.kts

@@ -27,6 +27,8 @@ dependencies {
     testImplementation("com.hypixel.hytale:Server:$hytaleServerVersion")
     testImplementation("org.junit.jupiter:junit-jupiter:5.10.0")
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+    testImplementation("org.mockito:mockito-core:5.14.2")
+    testImplementation("org.assertj:assertj-core:3.26.3")
 }
 
 java {
@@ -91,5 +93,7 @@ tasks {
 
     test {
         useJUnitPlatform()
+        // Byte Buddy (Mockito) ne supporte pas encore Java 25 officiellement — flag experimental requis.
+        jvmArgs("-Dnet.bytebuddy.experimental=true")
     }
 }