fix(tui): post-check cursor visibility in viewport during Loading

crates/tui/src/app.rs

@@ -281,9 +281,37 @@ impl App {
             self.viewport_cache.entries.push(entry);
         }
 
+        // Post-check: ensure cursor_line is within rendered entries (Loading + JSON expansion)
+        if self.is_loading() {
+            let entries = &self.viewport_cache.entries;
+            let last_entry_end = self.viewport_cache.logical_start
+                + entries.len()
+                + entries.last().map(|e| e.visual_height).unwrap_or(0).saturating_sub(1);
+            let first_entry_start = self.viewport_cache.logical_start;
+            if self.cursor_line >= last_entry_end || self.cursor_line < first_entry_start {
+                self.v_offset = self.cursor_line;
+                self.viewport_cache.entries.clear();
+                self.viewport_cache.logical_start = self.cursor_line;
+                self.fill_viewport_entries(self.cursor_line, width, viewport_height);
+            }
+        }
+
         (start_logical, offset_in_line)
     }
 
+    fn fill_viewport_entries(&mut self, start_logical: usize, width: usize, viewport_height: usize) {
+        let total = self.total_lines();
+        let mut rows_remaining = viewport_height;
+        for line_idx in start_logical..total {
+            if rows_remaining == 0 {
+                break;
+            }
+            let entry = self.compute_line_entry(line_idx, width);
+            rows_remaining = rows_remaining.saturating_sub(entry.visual_height);
+            self.viewport_cache.entries.push(entry);
+        }
+    }
+
     /// Compute total visual rows (cached, lazily evaluated).
     /// Returns `total_lines` for sampling mode (1:1 mapping).
     fn total_visual_rows(&mut self) -> usize {