feat: finished basic warning system

nodes can now register warnings to prevent running the program

ref: N25B-450

src/pages/VisProgPage/visualProgrammingUI/nodes/StartNode.tsx

@@ -1,12 +1,15 @@
 import {
   type NodeProps,
   Position,
-  type Node,
+  type Node, useNodeConnections
 } from '@xyflow/react';
+import {useEffect} from "react";
 import { Toolbar } from '../components/NodeComponents';
 import styles from '../../VisProg.module.css';
 import {SingleConnectionHandle} from "../components/RuleBasedHandle.tsx";
+import type {EditorWarning} from "../EditorWarnings.tsx";
 import {allowOnlyConnectionsFromHandle} from "../HandleRules.ts";
+import useFlowStore from "../VisProgStores.tsx";
 
 
 export type StartNodeData = {
@@ -25,6 +28,29 @@ export type StartNode = Node<StartNodeData>
  * @returns React.JSX.Element
  */
 export default function StartNode(props: NodeProps<StartNode>) {
+  const {registerWarning, unregisterWarning} = useFlowStore.getState();
+  const connections = useNodeConnections({
+    id: props.id,
+    handleId: 'source'
+  })
+
+  useEffect(() => {
+    const noConnectionWarning : EditorWarning = {
+      scope: {
+        id: props.id,
+        handleId: 'source'
+      },
+      type: 'MISSING_OUTPUT',
+      severity: "ERROR",
+      description: "the startNode does not have an outgoing connection to a phaseNode"
+    }
+
+    if (connections.length === 0) { registerWarning(noConnectionWarning); }
+    else { unregisterWarning(props.id, `${noConnectionWarning.type}:source`); }
+  }, [connections.length, props.id, registerWarning, unregisterWarning]);
+  
+
+
   return (
     <>
       <Toolbar nodeId={props.id} allowDelete={false}/>