fix(win32): restore mouse moves, add enter and leave, capture drags, and close and destroy windows cleanly

Win32
- WM_MOUSEMOVE is handled again: c9ebd44 put the WM_CHAR case where it
  was, so currentMousePos stopped following the mouse and onMouseMove
  never fired. Positions are read signed (GET_X_LPARAM), since under
  capture they run past the client area.
- onMouseEnter and onMouseLeave. The first move over the client area
  after a leave is the enter, and arms the TME_LEAVE whose WM_MOUSELEAVE
  is the leave. An enter counts only once that is armed, a leave only
  after an enter, and a move past the client area is a move only.
- A press captures the mouse, so a drag that leaves the window still
  sends its moves and its release, as Wayland's implicit grab does.
  Losing the capture releases what is held, and a button-up without its
  press fires nothing.
- WM_CLOSE fires onClose and clears open, as xdg_toplevel.close does,
  instead of destroying the HWND under the swapchain. WM_DESTROY no
  longer posts WM_QUIT, which nothing read.
- ~Window detaches the HWND and destroys it. It stayed on screen, and its
  messages went to the freed Window. WndProc hands messages without a
  Window to DefWindowProc, and looks the Window up again after an event
  that more work follows, in case a listener destroyed it.
- The constructor's message pump leaves input queued for StartSync: the
  WM_MOUSEMOVE sent when a window appears under the cursor made an
  onMouseEnter nobody could hear yet. The mouse state is reset before
  the platform code, no longer after it.
- A window after the first finds its class registered, which showed an
  error box.
- The wheel remainder is the window's, no longer a function static that
  every window shared, and a leave drops it.

Window
- PointerEnter, PointerMove, PointerLeave and PointerScroll hold the rules
  both native backends report the pointer by. An enter puts the entry
  position in currentMousePos before onMouseEnter fires, and is followed
  by a move, on Wayland too now. scrollRemainder replaces
  Device::scrollDetentRemainder, and mouseInside is shared.

Tests
- PointerEnterLeave: enter, move and leave through the wl_pointer
  callbacks.
- PointerWin32: posts a real HWND the messages above and pumps them as
  StartSync does. Built for x86_64-w64-mingw32 it runs under Wine, and is
  skipped where Wine is not on PATH.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

interfaces/Crafter.Graphics-Window.cppm

@@ -122,8 +122,9 @@ export namespace Crafter {
         // WheelEvent deltas by the per-deltaMode detent size, Wayland
         // divides the axis value by libinput's 15-units-per-detent,
         // Win32 divides by WHEEL_DELTA. Sub-detent motion (smooth-scroll
-        // touchpads, free-spinning wheels) is accumulated backend-side
-        // until a whole detent is reached.
+        // touchpads, free-spinning wheels) is accumulated until a whole
+        // detent is reached — by PointerScroll natively, by dom-env.js in
+        // the browser — and dropped when the pointer leaves.
         Event<std::uint32_t> onMouseScroll;
         // Touch, from the seat's wl_touch. The first finger down also drives
         // currentMousePos and the left-button events until it lifts, so a
@@ -144,6 +145,28 @@ export namespace Crafter {
         bool mouseLeftHeld = false;
         bool mouseRightHeld = false;
 
+        #ifndef CRAFTER_GRAPHICS_WINDOW_DOM
+        // The pointer is over the window: set before onMouseEnter fires,
+        // cleared before onMouseLeave does.
+        bool mouseInside = false;
+        // The part of a wheel detent PointerScroll has not reported yet.
+        double scrollRemainder = 0.0;
+        // The backends report the pointer through these, so that enter,
+        // move, leave and scroll mean the same on each. PointerEnter puts
+        // the entry position in currentMousePos before onMouseEnter fires,
+        // and an enter is a move too: the backend follows it with
+        // PointerMove. PointerLeave drops the scroll remainder, and fires
+        // only after an enter. Each fires its event last, since a listener
+        // may destroy the window, so a backend that makes a second call
+        // first checks that the window still exists.
+        void PointerEnter(Vector<float, 2> position);
+        void PointerMove(Vector<float, 2> position);
+        void PointerLeave();
+        // Adds wheel motion in detents, fractions included, and fires
+        // onMouseScroll for each whole detent it adds up to.
+        void PointerScroll(double detents);
+        #endif
+
         Window() = default;
         Window(std::uint32_t width, std::uint32_t height);
         Window(std::uint32_t width, std::uint32_t height, const std::string_view title);
@@ -160,8 +183,10 @@ export namespace Crafter {
         // the swapchain and the Vulkan surface, then (Wayland) the cursor,
         // viewport, fractional scale, decoration, xdg toplevel, xdg surface
         // and wl_surface, and the window leaves Device::windows and the
-        // focus pointers — so a window can be closed and another created,
-        // which a resident app does on every hide and show.
+        // focus pointers, or (Win32) the HWND, detached from this Window
+        // first so that no message still meant for it arrives here — so a
+        // window can be closed and another created, which a resident app
+        // does on every hide and show.
         ~Window();
 
         // Enter the platform event loop and never return. In DOM mode this
@@ -232,6 +257,7 @@ export namespace Crafter {
         #endif
 
         #ifdef CRAFTER_GRAPHICS_WINDOW_WIN32
+        HWND hwnd = nullptr;
         HBITMAP cursorBitmap = nullptr;
         HCURSOR cursorHandle = nullptr;
         std::uint16_t cursorSizeX = 0;