feat: multi-material overlays, presentation guides, and release prebuilds

Align control/presentation with presentation screen rect and darkness z-order; sync window titles and session window cleanup. Pack Win/Mac/Linux with npmRebuild disabled and release-native-prep for classic-level and sharp.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/shared/sceneOverlay/overlayViewport.ts

@@ -0,0 +1,21 @@
+import type { CSSProperties } from 'react';
+
+export type SceneOverlayViewport = {
+  x: number;
+  y: number;
+  w: number;
+  h: number;
+};
+
+export function overlayRootStyle(viewport: SceneOverlayViewport | null | undefined): CSSProperties | undefined {
+  if (!viewport || viewport.w <= 0 || viewport.h <= 0) return undefined;
+  return {
+    left: viewport.x,
+    top: viewport.y,
+    width: viewport.w,
+    height: viewport.h,
+    right: 'auto',
+    bottom: 'auto',
+    overflow: 'hidden',
+  };
+}