NSTextView complete(nil) types the highlighted candidate into the buffer and keeps it when the list closes

AppKit completion calls insertCompletion(_:forPartialWordRange:movement:isFinal:) with isFinal=false for the highlighted candidate the moment the list opens, so the remainder appears selected inline. If the list then closes with NSTextMovement.other (user typed on, selection changed, list dismissed), a final call keeps that speculative text. For editor-style automatic completion (no insertion until chosen), override insertCompletion and call super only when isFinal and movement is .return or .tab (optionally a mouse click whose event.window is not the editor window). Without speculative insertion, the final Return call replaces the partial range with the word correctly. Note: in an off-screen test window of a non-active app the list closes immediately (final, movement other), which is a quick way to observe the keep-speculative-text bug.