Add linear mode (#6670)

![linear-mode](https://github.com/user-attachments/assets/d1aa078a-00a8-4e71-86d5-ee929b269c90)

See also: #6642

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6670-Add-linear-mode-2aa6d73d365081d08887e4a6db3a8fa0)
by [Unito](https://www.unito.io)

src/renderer/core/canvas/canvasStore.ts

@@ -40,6 +40,8 @@ export const useCanvasStore = defineStore('canvas', () => {
   // Reactive scale percentage that syncs with app.canvas.ds.scale
   const appScalePercentage = ref(100)
 
+  const linearMode = ref(false)
+
   // Set up scale synchronization when canvas is available
   let originalOnChanged: ((scale: number, offset: Point) => void) | undefined =
     undefined
@@ -138,6 +140,7 @@ export const useCanvasStore = defineStore('canvas', () => {
     groupSelected,
     rerouteSelected,
     appScalePercentage,
+    linearMode,
     updateSelectedItems,
     getCanvas,
     setAppZoomFromPercentage,