refactor: migrate elements by schema in restore

packages/element/src/newElement.ts

@@ -50,6 +50,8 @@ import type {
   ExcalidrawLineElement,
 } from "./types";
 
+const ELEMENT_SCHEMA_VERSION = 2;
+
 export type ElementConstructorOpts = MarkOptional<
   Omit<ExcalidrawGenericElement, "id" | "type" | "isDeleted" | "updated">,
   | "width"
@@ -144,6 +146,7 @@ const _newElementBase = <T extends ExcalidrawElement>(
     roundness,
     seed: rest.seed ?? randomInteger(),
     version: rest.version || 1,
+    schemaVersion: rest.schemaVersion ?? ELEMENT_SCHEMA_VERSION,
     versionNonce: rest.versionNonce ?? 0,
     isDeleted: false as false,
     boundElements,

packages/element/src/types.ts

@@ -58,6 +58,8 @@ type _ExcalidrawElementBase = Readonly<{
   /** Integer that is sequentially incremented on each change. Used to reconcile
       elements during collaboration or when saving to server. */
   version: number;
+  /** Schema version hint used for per-element migration on restore. */
+  schemaVersion?: number;
   /** Random integer that is regenerated on each change.
       Used for deterministic reconciliation of updates during collaboration,
       in case the versions (see above) are identical. */