Update CLAUDE.md to reflect Paper API + JUnit 5 + MockBukkit migration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tastybento

CLAUDE.md

@@ -4,7 +4,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Project Overview
 
-AcidIsland is a BentoBox GameModeAddon for Minecraft (Spigot/Paper). It implements a Skyblock-like game mode where the ocean is acid that damages players, mobs, and items. Requires BentoBox as the parent plugin framework.
+AcidIsland is a BentoBox GameModeAddon for Minecraft (Paper). It implements a Skyblock-like game mode where the ocean is acid that damages players, mobs, and items. Requires BentoBox 3.12.0+ as the parent plugin framework.
 
 ## Build Commands
 
@@ -30,18 +30,54 @@ This is a BentoBox addon, not a standalone plugin. The lifecycle flows through:
 ### Key Packages
 
 - **`listeners/`** — `AcidEffect` is the core gameplay listener handling all acid damage (players, mobs, items, armor protection, potion effects, Essentials integration). `LavaCheck` prevents normal stone generation from lava+acid water.
-- **`world/`** — `ChunkGeneratorWorld` generates ocean floor terrain using Perlin noise. `AcidTask` is a repeating BukkitRunnable applying acid damage to entities in water. `AcidBiomeProvider` provides biomes per environment type.
+- **`world/`** — `ChunkGeneratorWorld` generates ocean floor terrain using Perlin noise. `AcidTask` is a repeating task applying acid damage to entities in water. `AcidBiomeProvider` provides biomes per environment type.
 - **`events/`** — Custom Bukkit events (`AcidEvent`, `AcidRainEvent`, `EntityDamageByAcidEvent`, etc.) that are cancellable, allowing other plugins to modify acid behavior.
 
 ### Testing
 
-Tests use **JUnit 5 + Mockito**. For static Bukkit methods, use Mockito static mocking via `Mockito.mockStatic` rather than adding new JUnit 4/PowerMock-based tests. The Surefire plugin is configured with extensive `--add-opens` JVM args for Java 21 compatibility. `ServerMocks` utility class provides reusable mock server setup.
+Tests use **JUnit 5 + MockBukkit + Mockito 5**. The standard pattern for each test class:
+
+```java
+@ExtendWith(MockitoExtension.class)
+@MockitoSettings(strictness = Strictness.LENIENT)
+public class MyTest {
+    private ServerMock server;
+    private MockedStatic<Bukkit> mockedBukkit;
+
+    @BeforeEach
+    public void setUp() {
+        server = MockBukkit.mock();  // always first
+        mockedBukkit = Mockito.mockStatic(Bukkit.class, Mockito.RETURNS_DEEP_STUBS);
+        mockedBukkit.when(Bukkit::getMinecraftVersion).thenReturn("1.21.11");
+        mockedBukkit.when(Bukkit::getServer).thenReturn(server);
+        // ...
+    }
+
+    @AfterEach
+    public void tearDown() {
+        mockedBukkit.closeOnDemand();
+        MockBukkit.unmock();
+    }
+}
+```
+
+Key rules:
+- **Do NOT call `Mockito.framework().clearInlineMocks()` in `@AfterEach`** — it disables `@BeforeAll` mocks and interferes with MockitoExtension's mock lifecycle for subsequent tests.
+- Always mock `Bukkit::getMinecraftVersion` — BentoBox 3.12.0 calls it in a static initializer and Paper API is required for it to exist on the classpath.
+- `paper-api` is a `provided` dependency (not `spigot-api`) — this is what puts `getMinecraftVersion()` on the compile/test classpath.
+- MockBukkit's JUnit transitive deps are excluded in `pom.xml` to avoid JUnit 6 version conflicts with surefire.
+- Do not use `new ItemStack(Material.AIR)` in tests — use `null` for empty armor slots; Paper 1.21's ItemStack handles AIR differently.
+- Do not reference `world.bentobox.bentobox.lists.Flags` static fields in tests — the class static initializer requires full BentoBox initialization. Use the string flag ID instead (e.g., `"ANIMAL_NATURAL_SPAWN"`).
+
+### Locales
+
+All 24 locale files use **MiniMessage format** (e.g., `<red>`, `<dark_blue>`). Legacy `&` color codes must not be used. BentoBox 3.12.0+ is required for MiniMessage support.
 
 ### Configuration
 
 - `src/main/resources/config.yml` — Default config with acid damage values, rain settings, potion effects, world generation params
-- `src/main/resources/addon.yml` — BentoBox addon metadata and permissions
-- `src/main/resources/locales/` — 24 language translation files
+- `src/main/resources/addon.yml` — BentoBox addon metadata and permissions (requires `api-version: 3.12.0`)
+- `src/main/resources/locales/` — 24 language translation files (MiniMessage format)
 - `src/main/resources/blueprints/` — Island templates (overworld, nether, end)
 
 ## CI