Sync node help with selection and add watcher tests (#7105)

## Summary
- add a watcher to sync the node help panel with the currently selected
node
- add unit coverage for help auto-switching and guard cases

## Testing
- pnpm typecheck
- pnpm lint:fix
- pnpm exec vitest
tests-ui/tests/composables/graph/useSelectionState.test.ts

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7105-Sync-node-help-with-selection-and-add-watcher-tests-2bd6d73d36508140b5acd3f3c65c5680)
by [Unito](https://www.unito.io)

src/composables/graph/useSelectionState.ts

@@ -105,12 +105,11 @@ export function useSelectionState() {
 
     const isSidebarActive =
       sidebarTabStore.activeSidebarTabId === nodeLibraryTabId
-    const currentHelpNode: any = nodeHelpStore.currentHelpNode
+    const currentHelpNode = nodeHelpStore.currentHelpNode
     const isSameNodeHelpOpen =
       isSidebarActive &&
       nodeHelpStore.isHelpOpen &&
-      currentHelpNode &&
-      currentHelpNode.nodePath === def.nodePath
+      currentHelpNode?.nodePath === def.nodePath
 
     if (isSameNodeHelpOpen) {
       nodeHelpStore.closeHelp()