feat(examples): four runnable plugin examples

- player-load: load-on-join (PlayerReadyEvent → IO → modify).
- async-moderation: IAsyncEvent → coroutine bridge for chat moderation.
- periodic-leaderboard: pluginScope loop with parallel reads.
- bounty-board: kitchen-sink demo exercising every v0.1 primitive.

examples/README.md

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+# Examples
+
+Four runnable plugin sketches built as Gradle composite builds — they
+consume the in-development library directly via `includeBuild("../..")`,
+so editing the lib and rebuilding an example picks up the change without
+publishing.
+
+| Example | Pattern |
+|---|---|
+| [`player-load/`](player-load/) | Load player JSON on `PlayerReadyEvent`, mutate a component on the world thread. |
+| [`async-moderation/`](async-moderation/) | `IAsyncEvent` (`PlayerChatEvent`) bridged to coroutines, off-thread check, conditional `modify` + event cancel. |
+| [`periodic-leaderboard/`](periodic-leaderboard/) | Plugin-scoped periodic loop with parallel `read` over players. |
+| [`bounty-board/`](bounty-board/) | The kitchen sink — exercises every public Async primitive. |
+
+## Build any of them
+
+```bash
+cd examples/<name>
+./gradlew shadowJar
+# → build/libs/<name>.jar
+```
+
+Drop the JAR in your dev server's `mods/`.
+
+## How the composite wiring works
+
+Each example's `settings.gradle.kts` does:
+
+```kotlin
+includeBuild("../..") {
+    dependencySubstitution {
+        substitute(module("com.mythlane:async"))
+            .using(project(":dist"))
+    }
+}
+```
+
+So `implementation("com.mythlane:async:0.1.0-SNAPSHOT")` resolves to the
+local `:dist` project — no Maven publication required during dev.
+
+## What's stubbed
+
+Each example contains `TODO()` markers in two places:
+
+1. **Custom `Component<EntityStore>` registration.** Declaring `Wallet`,
+   `PlayerStats`, etc. on `EntityStore.REGISTRY` is plugin-specific and not
+   part of what Async does. Async only consumes the resulting `ComponentType`
+   via `ComponentRegistry.register<T>(...)`.
+
+2. **Online-player accessors** like `onlinePlayerRefs()` and
+   `broadcastToAllWorlds(...)`. These iterate `Universe.get()` /
+   `world.players` in whatever shape your plugin needs.
+
+Wire those to your dev server and the examples become fully runnable. The
+Async-side calls (`installAsync()`, `playerScope`, `modify<T>`,
+`PlayerRef.toEntityHandle()`, etc.) are accurate as-shipped.