feat(window): 滚轮事件下传与 Terminal 滚动

- desk 协议新增 DESK_MOUSE_WHEEL；window 新增 EVENT_TYPE_WHEEL
- Explorer 汇总一批鼠标包的 wheel 增量，投给光标下的窗口
  （窗口内坐标；任务栏区域不投递）
- InputEvent.button 承载滚轮有符号增量（uint8 编码，消费方按 int8 解码）
- vpui.Text 处理 WHEEL：每次滚动 3 行，按“输出行 + 输入行”总行数钳制，
  并同步滚动条；输入行仍保持在可视区内

Apps/Explorer/desk_server.vp

@@ -1827,6 +1827,11 @@ class DeskServer:
                 viperlib.snprintf(&_mb, 128, "[explorer] mouse pkt n=%d btn=%d\n", mn, int(mp[0]))
                 devfs.serial_puts(&_mb)
             moved: int = 0
+            wheel: int = 0
+            if mn >= 10:
+                wv: int = int(mp[9])
+                if wv >= 128: wv = wv - 256
+                wheel = wheel + wv
             if mn >= 9:
                 moved = self._move_cursor(int(*(int32*(uint64(&mp) + uint64(1)))),
                                           int(*(int32*(uint64(&mp) + uint64(5)))))
@@ -1848,7 +1853,19 @@ class DeskServer:
                 bi: int = int(mp[0]) & 1
                 if bi != 0 and cur == 0: saw_press = 1
                 cur = bi
+                if mn >= 10:
+                    wv2: int = int(mp[9])
+                    if wv2 >= 128: wv2 = wv2 - 256
+                    wheel = wheel + wv2
                 mn = fs.read(self.mfd, &mp, uint32(16))
+            if wheel != 0:
+                # 滚轮：投给光标下那个窗口（窗口内坐标），由控件决定滚动行为。
+                hw: int = self.hit_test(self.cx, self.cy)
+                if hw >= 0:
+                    hs: desk.WinSlot* = self.slot(hw)
+                    self.push_event(hw, uint32(desk.DESK_EVT_MOUSE),
+                                    desk.DESK_MOUSE_WHEEL,
+                                    self.cx - hs.ux, self.cy - hs.uy - TITLE_H - TITLE_GAP, wheel)
             if moved != 0:
                 self._mark_cursor_at(self.pcy)
                 self._mark_cursor_at(self.cy)

vpsdk/desk.vp

@@ -65,6 +65,7 @@ define DESK_EVT_RESIZE   = 105   # a=w b=h
 define DESK_MOUSE_PRESS   = 1
 define DESK_MOUSE_RELEASE = 2
 define DESK_MOUSE_HOVER   = 3
+define DESK_MOUSE_WHEEL   = 4     # d = 滚轮增量（有符号）
 
 
 @__attribute__(packed)

vpsdk/vpui.vp

@@ -1294,6 +1294,19 @@ virtual class Text(Widget):
                     tk2: Tk* = self.tk
                     tk2.focused_widget = None
                     return 1
+        elif etype == window.EVENT_TYPE_WHEEL:
+            if self.contains(ex, ey):
+                w: int = int(evt.button)
+                if w >= 128: w = w - 256
+                vis: int = self._visible_lines()
+                self.scroll_offset = self.scroll_offset - w * 3
+                max_off: int = self.line_count + 1 - vis
+                if max_off < 0: max_off = 0
+                if self.scroll_offset < 0: self.scroll_offset = 0
+                if self.scroll_offset > max_off: self.scroll_offset = max_off
+                self._update_scrollbar()
+                return 1
+            return 0
         elif etype == window.EVENT_TYPE_KEY:
             if self.focused:
                 ebtn2: uint8 = evt.button

vpsdk/window.vp

@@ -20,6 +20,7 @@ define EVENT_TYPE_KEY = 5
 define EVENT_TYPE_KEY_RELEASE = 6
 define EVENT_TYPE_PING = 7
 define EVENT_TYPE_RESIZE = 8
+define EVENT_TYPE_WHEEL = 9
 
 define KEY_STATE_PRESS = 1
 define KEY_STATE_RELEASE = 2
@@ -229,6 +230,8 @@ def poll_event(evt: InputEvent*) -> int:
             evt.type = uint32(EVENT_TYPE_CLICK)
         elif kind == desk.DESK_MOUSE_RELEASE:
             evt.type = uint32(EVENT_TYPE_RELEASE)
+        elif kind == desk.DESK_MOUSE_WHEEL:
+            evt.type = uint32(EVENT_TYPE_WHEEL)
         else:
             evt.type = uint32(EVENT_TYPE_HOVER)
         evt.x = _evt.b                  # 窗口内坐标