fix: fix Terminal zoom inconsistency

kernel/src/Api/BuildNo.hpp

@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 107
+#define MONTAUK_BUILD_NUMBER 108

programs/include/gui/terminal.hpp

@@ -795,11 +795,21 @@ static inline void terminal_resize(TerminalState* t, int new_cols, int new_rows)
         }
     }
 
-    int new_scrollback = keep - new_rows;
+    // Anchor the new visible region to the cursor's line. Treating the bottom
+    // new_rows of kept content as the screen (the naive keep - new_rows) only
+    // works when the screen is full: with a partly filled screen -- e.g. a
+    // shell prompt a few lines down with blank rows below it -- it would push
+    // the real text up into scrollback and drop the view onto the blank region,
+    // so a zoom appears to scroll down and strands the cursor in empty space.
+    // Instead pin the cursor to the bottom row when there is enough history
+    // above it, otherwise keep the content anchored at the top.
+    int abs_cursor_y = t->scrollback_lines + t->cursor_y - discard;
+    if (abs_cursor_y < 0) abs_cursor_y = 0;
+    int new_scrollback = abs_cursor_y - (new_rows - 1);
     if (new_scrollback < 0) new_scrollback = 0;
+    if (new_scrollback > t->max_scrollback) new_scrollback = t->max_scrollback;
 
     // Adjust cursor
-    int abs_cursor_y = t->scrollback_lines + t->cursor_y - discard;
     int new_cursor_y = abs_cursor_y - new_scrollback;
     if (new_cursor_y < 0) new_cursor_y = 0;
     if (new_cursor_y >= new_rows) new_cursor_y = new_rows - 1;