fix: reset viewport on window resize to prevent content jump and loss

kaku-gui/src/termwindow/resize.rs

@@ -555,6 +555,12 @@ impl super::TermWindow {
                     tab.resize(size);
                 }
             }
+            for tab in window.iter() {
+                for pos in tab.iter_panes_ignoring_zoom() {
+                    let mut state = self.pane_state(pos.pane.pane_id());
+                    state.viewport = None;
+                }
+            }
         };
         if live {
             self.pending_pty_flush_after_resize = true;

term/src/screen.rs

@@ -224,10 +224,18 @@ impl Screen {
         // pre-prune blank lines that range from the cursor position to the end of the display;
         // this avoids growing the scrollback size when rapidly switching between normal and
         // maximized states.
+        // Limit pruning to lines beyond the visible viewport to avoid losing
+        // scrollback content during repeated resizes.
         let cursor_phys = self.phys_row(cursor.y);
+        let max_prune = self.lines.len().saturating_sub(self.physical_rows);
+        let mut pruned = 0;
         for _ in cursor_phys + 1..self.lines.len() {
+            if pruned >= max_prune {
+                break;
+            }
             if self.lines.back().map(Line::is_whitespace).unwrap_or(false) {
                 self.lines.pop_back();
+                pruned += 1;
             }
         }