feat: implement mode 1048 for saving/restoring cursor position

src/terminal/modes.zig

@@ -223,6 +223,7 @@ const entries: []const ModeEntry = &.{
     .{ .name = "alt_sends_escape", .value = 1039 },
     .{ .name = "reverse_wrap_extended", .value = 1045 },
     .{ .name = "alt_screen", .value = 1047 },
+    .{ .name = "save_cursor", .value = 1048 },
     .{ .name = "alt_screen_save_cursor_clear_enter", .value = 1049 },
     .{ .name = "bracketed_paste", .value = 2004 },
     .{ .name = "synchronized_output", .value = 2026 },

src/termio/stream_handler.zig

@@ -597,6 +597,18 @@ pub const StreamHandler = struct {
                 try self.queueRender();
             },
 
+            // Mode 1048 is xterm's conditional save cursor depending
+            // on if alt screen is enabled or not (at the terminal emulator
+            // level). Alt screen is always enabled for us so this just
+            // does a save/restore cursor.
+            .save_cursor => {
+                if (enabled) {
+                    self.terminal.saveCursor();
+                } else {
+                    try self.terminal.restoreCursor();
+                }
+            },
+
             // Force resize back to the window size
             .enable_mode_3 => {
                 const grid_size = self.size.grid();