feat: full screen node

frontend/src/lib/flowContext.tsx

@@ -22,6 +22,9 @@ export type FlowContextValue = {
     isValidConnection: (connection: Connection) => boolean
     /** Set by FlowKeyboardShortcuts so Node menubar can trigger paste / fit view. */
     flowActionsRef: React.MutableRefObject<FlowActions | null>
+    /** When set, graph centers on this node and a fullscreen dialog shows the node. Cleared on close. */
+    fullscreenNodeId: string | null
+    setFullscreenNodeId: (id: string | null) => void
 }
 
 const FlowContext = React.createContext<FlowContextValue | null>(null)