fix(overlay): prevent Windows mouse lag during click-through tracking (#201)

src/core/services/overlay-click-through.ts

@@ -0,0 +1,27 @@
+type ClickThroughWindow = {
+  setIgnoreMouseEvents: (ignore: boolean, options?: { forward?: boolean }) => void;
+};
+
+/**
+ * Puts an overlay window into click-through mode. Forwarded mouse-move ({ forward: true }) is
+ * what lets renderer hover tracking wake a click-through overlay, but on Windows Electron
+ * implements it with a global WH_MOUSE_LL hook whose callback runs on the main-process message
+ * loop, so any main-thread stall delays mouse input system-wide (electron/electron#10183).
+ * Windows instead wakes the overlay via the main-process cursor poll
+ * (tickWindowsOverlayPointerInteraction), so no forwarding is requested there. macOS still
+ * needs forwarding for renderer hover tracking; Linux ignores the flag entirely
+ * (electron/electron#16777).
+ *
+ * Pass isWindowsPlatform when the caller already carries a platform flag (tests simulate
+ * platforms through it); otherwise the real process.platform decides.
+ */
+export function applyOverlayClickThrough(
+  window: ClickThroughWindow,
+  isWindowsPlatform?: boolean,
+): void {
+  if (isWindowsPlatform ?? process.platform === 'win32') {
+    window.setIgnoreMouseEvents(true);
+  } else {
+    window.setIgnoreMouseEvents(true, { forward: true });
+  }
+}