feat(canvas): 画布工作台 - 新增生成副本并修复大型画布性能、素材同步与删除校验

统一图片与视频副本的生成落点并保留参考连接。\n优化大型画布节点虚拟化、媒体懒加载、拖拽与详情进入路径。\n修复素材主版本 ID 同步及删除时的画布独立引用校验。

web/src/lib/canvas/canvas-node-timestamps.ts

@@ -50,10 +50,15 @@ export function normalizeCanvasNodeTimestamps(nodes: CanvasNodeData[], fallback:
 
 export function stampCanvasNodeChanges(previousNodes: CanvasNodeData[], nextNodes: CanvasNodeData[], now = new Date().toISOString()) {
     if (previousNodes === nextNodes) return previousNodes;
-    const previousById = new Map(previousNodes.map((node) => [node.id, node]));
+    // Most canvas edits preserve order and replace one node. Avoid allocating a
+    // 50k-entry id map and comparing metadata for every untouched node in that
+    // hot path. The map fallback still handles inserts, deletes and reorders.
+    const sameOrder = previousNodes.length === nextNodes.length && previousNodes.every((node, index) => node.id === nextNodes[index]?.id);
+    const previousById = sameOrder ? null : new Map(previousNodes.map((node) => [node.id, node]));
     let changed = false;
-    const stamped = nextNodes.map((node) => {
-        const previous = previousById.get(node.id);
+    const stamped = nextNodes.map((node, index) => {
+        const previous = sameOrder ? previousNodes[index] : previousById?.get(node.id);
+        if (previous === node) return node;
         const createdAt = canvasNodeCreatedAt(node, canvasNodeCreatedAt(previous || node, now)) || now;
         const meaningfulChange = previous ? canvasNodeMeaningfullyChanged(previous, node) : false;
         const updatedAt = previous
@@ -68,6 +73,33 @@ export function stampCanvasNodeChanges(previousNodes: CanvasNodeData[], nextNode
     return changed ? stamped : nextNodes;
 }
 
+/**
+ * Update one node without routing through the generic full-array timestamp
+ * reconciliation. This is used by media metadata callbacks, which can fire
+ * in bursts while a large canvas is first becoming visible.
+ */
+export function updateCanvasNode(nodes: CanvasNodeData[], nodeId: string, update: (node: CanvasNodeData) => CanvasNodeData, now = new Date().toISOString()) {
+    return updateCanvasNodes(nodes, new Map([[nodeId, update]]), now);
+}
+
+export function updateCanvasNodes(nodes: CanvasNodeData[], updates: ReadonlyMap<string, (node: CanvasNodeData) => CanvasNodeData>, now = new Date().toISOString()) {
+    if (!updates.size) return nodes;
+    let changed = false;
+    const next = nodes.map((current) => {
+        const update = updates.get(current.id);
+        if (!update) return current;
+        const updated = update(current);
+        if (updated === current) return current;
+        changed = true;
+        const createdAt = canvasNodeCreatedAt(updated, canvasNodeCreatedAt(current, now)) || now;
+        const updatedAt = canvasNodeMeaningfullyChanged(current, updated)
+            ? now
+            : canvasNodeUpdatedAt(updated, canvasNodeUpdatedAt(current, createdAt)) || createdAt;
+        return updated.createdAt === createdAt && updated.updatedAt === updatedAt ? updated : { ...updated, createdAt, updatedAt };
+    });
+    return changed ? next : nodes;
+}
+
 function canvasNodeMeaningfullyChanged(previous: CanvasNodeData, next: CanvasNodeData) {
     if (
         previous.type !== next.type