swarm-ui: give the new-flow draft a route no flow id can take, and drop the dead hit-count rule

/notifications/new could be a saved flow's own page, so the draft now opens at
/notifications/draft/new, which has a segment more than any flow's route. The
placeholder id no longer needs reserving. The .notify-node-hits rule styled the
removed tree rows; nothing renders it.

frontend/packages/swarm-ui/src/pages/notifications/NotificationsPage.tsx

@@ -20,7 +20,7 @@ import {
 } from "../../ui/refresh-interval/RefreshInterval.js";
 import { fetchJson, usePolled } from "../../ui/polled/usePolled.js";
 import { Deliveries } from "./Deliveries.js";
-import { NEW_FLOW_ID } from "./FlowDraft.js";
+import { NEW_FLOW_PATH } from "./FlowDraft.js";
 import { FlowGraph } from "./FlowGraph.js";
 import { withBuiltin, type FlowsView } from "./FlowTypes.js";
 import {
@@ -91,8 +91,8 @@ export function NotificationsPage() {
   const draftFrom = (from?: string) =>
     navigate(
       from === undefined
-        ? `/notifications/${NEW_FLOW_ID}`
-        : `/notifications/${NEW_FLOW_ID}?from=${encodeURIComponent(from)}`,
+        ? NEW_FLOW_PATH
+        : `${NEW_FLOW_PATH}?from=${encodeURIComponent(from)}`,
     );
 
   return (