Document MobScores setup and development

CONTRIBUTING.md

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+# Contributing
+
+## Requirements
+
+- Java 25. The Gradle toolchain can download it automatically; `tools/build-plugin.sh` also provisions Temurin 25 under the project Gradle user home.
+- A recent Paper server for runtime testing.
+- The ScoreKeeper plugin, which is a required runtime dependency.
+
+## Build and Test
+
+From the project root:
+
+```sh
+./gradlew test
+./gradlew build
+```
+
+The distributable plugin JAR is written to `build/libs/`. To use the repository helper, run:
+
+```sh
+tools/build-plugin.sh
+```
+
+## Local Paper Testing
+
+Set `PAPER_VERSION` and `MINECRAFT_SERVER_PATH` in a local `.env` file at the MobScores project root, or export them in your shell. Set `MINECRAFT_ENV_FILE` if the helper scripts should load a shared environment file instead. Build ScoreKeeper and install it into the server first, then build and deploy MobScores:
+
+```sh
+tools/build-plugin.sh
+tools/deploy-plugin.sh
+```
+
+Start the server with `tools/start-server.sh`. The script downloads a stable Paper build when one is not already present. Review the server log for dependency and plugin-load errors, then test score-table configuration and mob-kill scoring in game. Back up the server before testing against a world with data you care about.
+
+## Configuration
+
+The default resource is `src/main/resources/config.yml`; Paper copies it to `plugins/MobScores/config.yml` on first startup. `ScoreTable` maps Bukkit `EntityType` names to integer point values. To change values on a test server, edit the generated config and restart the server.
+
+## Helper Scripts
+
+- `tools/build-plugin.sh` builds with Java 25.
+- `tools/deploy-plugin.sh` copies the latest non-`-all` JAR into `$MINECRAFT_SERVER_PATH/plugins/`.
+- `tools/start-server.sh` downloads/resolves and launches Paper using `.env` settings.
+- `tools/backup-server.sh` and `tools/restore-server.sh` manage server backups.
+- `tools/publish-local.sh` publishes the artifact to Maven Local for dependent plugin builds.