feat(lsp): support Java class file contents and improve definition navigation handling

- Add `_lsp_java_class_file_contents` request to fetch contents of compiled Java classes via LSP (`java/classFileContents`).
- Handle `java/classFileContents` responses by opening a new buffer with Java syntax highlighting and inserting the returned source.
- Update definition handling to pass URI and range, enabling precise cursor placement after navigation.
- Detect `jdt://` URIs in `textDocument/definition` responses and request class file contents instead of direct navigation.
- Move goto navigation logic into `LSPServerEventsMixin`, using event system to access the active view and position the cursor.
- Expose `emit` and `emit_to` to the response cache for event dispatching.
- Restrict completion activation to `USER_REQUESTED`.
- Add TODO note about mapping language IDs to dedicated response handlers.

plugins/code/ui/lsp_manager/controllers/lsp_controller_events.py

@@ -119,3 +119,11 @@ class LSPControllerEvents:
         params["position"]["character"]      = data["column"]
 
         GLib.idle_add( self.send_request, method, params )
+
+    def _lsp_java_class_file_contents(self, uri: str):
+        method = "java/classFileContents"
+        params = {
+            "uri": uri
+        }
+
+        GLib.idle_add( self.send_request, method, params )