terminal: test shrinking both axes with cursor past new bottom

Adds a PageList regression test exercising the underflow path fixed in
7fa6fffbc, and a libghostty-vt C API test mirroring the original repro
through ghostty_terminal_resize.

src/terminal/PageList.zig

@@ -10828,6 +10828,37 @@ test "PageList resize (no reflow) less rows and cols" {
     }
 }
 
+test "PageList resize less rows and cols cursor at bottom" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 80, 24, 0);
+    defer s.deinit();
+
+    const cursor_pin = try s.trackPin(s.pin(.{ .active = .{
+        .x = 0,
+        .y = s.rows - 1,
+    } }).?);
+    defer s.untrackPin(cursor_pin);
+
+    // Shrink both axes such that the original cursor.y is strictly past the
+    // new row count, so resizeWithoutReflow leaves self.rows < c.y + 1.
+    try s.resize(.{
+        .cols = 79,
+        .rows = 20,
+        .reflow = true,
+        .cursor = .{ .x = 0, .y = 23, .pin = cursor_pin },
+    });
+    try testing.expectEqual(@as(usize, 79), s.cols);
+    try testing.expectEqual(@as(usize, 20), s.rows);
+
+    // remaining_rows saturates to 0, so the cursor lands on the new bottom row.
+    try testing.expectEqual(point.Point{ .active = .{
+        .x = 0,
+        .y = s.rows - 1,
+    } }, s.pointFromPin(.active, cursor_pin.*).?);
+}
+
 test "PageList resize (no reflow) more rows and less cols" {
     const testing = std.testing;
     const alloc = testing.allocator;

src/terminal/c/terminal.zig

@@ -1005,6 +1005,30 @@ test "resize invalid value" {
     try testing.expectEqual(Result.invalid_value, resize(t, 80, 0, 9, 18));
 }
 
+test "resize shrinks both axes with cursor at bottom" {
+    var t: Terminal = null;
+    try testing.expectEqual(Result.success, new(
+        &lib.alloc.test_allocator,
+        &t,
+        .{
+            .cols = 80,
+            .rows = 24,
+            .max_scrollback = 0,
+        },
+    ));
+    defer free(t);
+
+    // CSI 24;1H -> park the cursor on the bottom row (1-based).
+    const move = "\x1b[24;1H";
+    vt_write(t, move, move.len);
+
+    // Shrink both axes; pre-resize cursor.y sits past the new bottom row.
+    // Previously this underflowed in PageList.resizeCols.
+    try testing.expectEqual(Result.success, resize(t, 79, 23, 8, 16));
+    try testing.expectEqual(79, t.?.terminal.cols);
+    try testing.expectEqual(23, t.?.terminal.rows);
+}
+
 test "mode_get and mode_set" {
     var t: Terminal = null;
     try testing.expectEqual(Result.success, new(