fix: reset diff caches on graph instance change

Clears nodeStatesCache, currentNodeIds, lastNodeCount, lastLinkCount,
and lastGraphVersion when getDataSource detects a new LGraph instance
(e.g. subgraph navigation). Prevents stale baselines from masking
connection/structure changes on the new graph.

Addresses: https://github.com/Comfy-Org/ComfyUI_frontend/pull/9912#discussion_r2934626767

src/renderer/extensions/minimap/composables/useMinimapGraph.ts

@@ -126,6 +126,11 @@ export function useMinimapGraph(
     if (cachedDataSource && cachedDataSourceGraph === g) {
       return cachedDataSource
     }
+    nodeStatesCache.clear()
+    currentNodeIds.clear()
+    lastNodeCount.value = 0
+    lastLinkCount = 0
+    lastGraphVersion = -1
     cachedDataSource = MinimapDataSourceFactory.create(g)
     cachedDataSourceGraph = g
     return cachedDataSource