feat(tree-sitter, views): initialize AST on focus and emit source view creation event

- Add set_ast helper to centralize Tree-sitter parsing logic
- Parse and attach AST on FocusedViewEvent and TextChangedEvent
- Request file from buffer on view focus before parsing
- Fix parser guard condition in get_parser (handle missing language properly)

- Emit CreatedSourceViewEvent when a new source view is added
- Register CreatedSourceViewEvent in DTO exports

- Update TODO:
  - Remove completed collapsible code blocks task
  - Add fix note for code block icon desync issue

chore:
- Add scaffolding for code_fold UI plugin
- Add created_source_view_event DTO

src/core/widgets/code/controllers/views/source_views_controller.py

@@ -111,6 +111,12 @@ class SourceViewsController(ControllerBase, list):
         self.signal_mapper.connect_signals(source_view)
 
         self.append(source_view)
+
+        event = Event_Factory.create_event(
+            "created_source_view", view = source_view
+        )
+        self.emit(event)
+
         return source_view
 
     def first_map_load(self):

src/libs/dto/code/events/__init__.py

@@ -6,6 +6,7 @@
 from .code_event import CodeEvent
 from .toggle_plugins_ui_event import TogglePluginsUiEvent
 from .create_source_view_event import CreateSourceViewEvent
+from .created_source_view_event import CreatedSourceViewEvent
 from .register_completer_event import RegisterCompleterEvent
 from .unregister_completer_event import UnregisterCompleterEvent
 from .register_provider_event import RegisterProviderEvent

src/libs/dto/code/events/created_source_view_event.py

@@ -0,0 +1,14 @@
+# Python imports
+from dataclasses import dataclass
+
+# Lib imports
+
+# Application imports
+from .code_event import CodeEvent
+from libs.dto.states.source_view_states import SourceViewStates
+
+
+
+@dataclass
+class CreatedSourceViewEvent(CodeEvent):
+    ...