fix: app mode widgets disappear after hard refresh (#9621)

## Summary

Fix all app mode widgets (including seed) disappearing after hard
refresh due to a race condition in `pruneLinearData` and a missing
reactivity dependency in `mappedSelections`.

## Changes

- **What**: Guard `pruneLinearData` with `!ChangeTracker.isLoadingGraph`
so inputs are preserved while `rootGraph.configure()` hasn't populated
nodes yet. Add `graphNodes` dependency to `mappedSelections` computed in
`LinearControls.vue` so it re-evaluates when the graph finishes
configuring.

## Review Focus

The core fix is a one-line guard change: `app.rootGraph &&
!ChangeTracker.isLoadingGraph` instead of just `app.rootGraph`. The
previous guard failed because `rootGraph` exists as an empty graph
during loading — `resolveNode()` returns `undefined` for all nodes and
everything gets filtered out.

Fixes COM-16193

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9621-fix-app-mode-widgets-disappear-after-hard-refresh-31d6d73d3650811193f5e1bc8f3c15c8)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

src/renderer/extensions/linearMode/LinearControls.vue

@@ -64,6 +64,7 @@ useEventListener(
 )
 
 const mappedSelections = computed(() => {
+  void graphNodes.value
   let unprocessedInputs = appModeStore.selectedInputs.flatMap(
     ([nodeId, widgetName]) => {
       const [node, widget] = resolveNodeWidget(nodeId, widgetName)