Improve asynchronous filesystem event processing

- queue and batch filesystem model updates on the main thread
  - process directory-tree updates and worker-affine listeners asynchronously
  - coalesce adjacent modified events for the same path
  - preserve captured file metadata across delayed event delivery
  - add event, path, and thread-affinity filters for listener subscriptions
  - configure optimized per-plugin filesystem subscriptions
  - make listener removal wait for active callbacks safely
  - handle self-removal without deadlocking
  - support allocation-free matching of moved source paths
  - synchronize project directory-tree mutations with active searches
  - centralize diff-view button visibility around find/replace state
  - improve code editor wrap-content and scrollbar sizing
  - add queue, listener, and filesystem-model regression tests

include/eepp/scene/event.hpp

@@ -132,6 +132,8 @@ class EE_API Event {
 		OnFocusWithinLoss,
 		OnItemsCountChange,
 		OnApply,
+		OnShowFindReplace,
+		OnHideFindReplace,
 		NoEvent = eeINDEX_NOT_FOUND
 	};
 

include/eepp/ui/models/filesystemmodel.hpp

@@ -224,6 +224,14 @@ class EE_API FileSystemModel : public Model {
 	 */
 	bool handleFileEvent( const FileEvent& event );
 
+	/**
+	 * @brief Processes a filesystem event using metadata captured when the event was received.
+	 *
+	 * This avoids querying the filesystem from the main thread and preserves the state observed by
+	 * an asynchronous listener even if a later event changes the path before this event is applied.
+	 */
+	bool handleFileEvent( const FileEvent& event, const FileInfo& file );
+
 	virtual bool isValid( const ModelIndex& index ) const override;
 
 	virtual bool classModelRoleEnabled() { return true; }
@@ -256,7 +264,9 @@ class EE_API FileSystemModel : public Model {
 
 	size_t getFileIndex( Node* parent, const FileInfo& file, const Node* excludedNode = nullptr );
 
-	bool handleFileEventLocked( const FileEvent& event );
+	bool handleFileEventLocked( const FileEvent& event, const FileInfo* preparedFile = nullptr );
+
+	bool handleFileEvent( const FileEvent& event, const FileInfo* preparedFile );
 
 	void setupColumnNames( Translator* translator );
 };

include/eepp/ui/tools/uidiffview.hpp

@@ -135,6 +135,7 @@ class EE_API UIDiffView : public UIWidget, public WidgetCommandExecuter {
 	void computeSubLineDiff( DiffLine& oldLine, DiffLine& newLine );
 	void updateEditorsText();
 	void updateButtonsText();
+	void updateButtonsVisibility();
 	void createImageViewers();
 	bool loadImageDiffFromPaths( const std::string& oldFilePath, const std::string& newFilePath );
 	void updateImageDiffView();

include/eepp/ui/uicodeeditor.hpp

@@ -869,6 +869,8 @@ class EE_API UICodeEditor : public UIWidget, public TextDocument::Client {
 
 	void setDynamicTheming( bool set );
 
+	const Tools::UIDocFindReplace* getFindReplace() const { return mFindReplace; }
+
   protected:
 	struct LastXOffset {
 		TextPosition position{ 0, 0 };