Fix: ESC[2J aus Frame-Rendering entfernt verhindert Scrollback

ESC[2J schiebt in iTerm2 den Bildschirminhalt bei jedem Aufruf
in den Scrollback-Puffer – 10x/Sekunde. Da render() ohnehin
jede Zelle überschreibt, genügt ESC[H (Cursor-Home).

asciiquarium_ng.py

@@ -121,10 +121,9 @@ class Canvas:
                     self._ck[row][col] = ck
 
     def render(self) -> str:
-        # \033[2J clears the entire terminal (not just our canvas width),
-        # preventing stale characters when the terminal is wider than self.cols
-        # or after a resize.  The full-canvas overwrite below keeps flicker minimal.
-        parts = ["\033[2J\033[H", RESET]
+        # \033[H homes the cursor; every cell is rewritten below so \033[2J is
+        # not needed and would push content into the scrollback on every frame.
+        parts = ["\033[H", RESET]
         sentinel = object()
         last_ck: object = sentinel
         for r in range(self.rows):