refactor: redesign plugin system and enhance message handling

- Move plugin and tool-related classes to a dedicated `Plugin-API` module.
- Introduce a new plugin lifecycle (`onInit`, `onEnable`, `onDisable`) and a more robust `Tool` API.
- Refactor `Core` to use `PrintAdvanceMessageHandler` for improved handling of assistant messages, tool responses, and errors.
- Rename `PluginLoader` to `Loader` and migrate it to `me.zacharias.chat.plugin.loader`.
- Update build configurations and Java toolchains across modules.
- Clean up obsolete plugin annotations and interfaces in the `Core` module.

gradle.properties

@@ -1,2 +1,3 @@
 # This is used in sub-project that dosent explicitly require the API sub-project to only include if thay shuld be included project wide.
-useAPI = true
+useAPI = true
+javaVersion = 26