Finally gets the routing working in a somewhat reasonable way

src/routes/_app/_authenticated/document.$documentId.$.tsx

@@ -0,0 +1,49 @@
+import { DocumentView } from "@/components/documents/DocumentView";
+import { DocumentLoader } from "@/context/document/DocumentLoader";
+import type { DocumentId } from "@/lib/types";
+import { RelationshipType } from "@/lib/types";
+import { createFileRoute } from "@tanstack/react-router";
+import * as z from "zod";
+
+export const Route = createFileRoute(
+  "/_app/_authenticated/document/$documentId/$",
+)({
+  component: RouteComponent,
+});
+
+const documentParams = z
+  .templateLiteral([
+    z.string(),
+    z.optional(z.literal("/")),
+    z.optional(z.string()),
+  ])
+  .pipe(
+    z.transform((path: string) => {
+      if (path === "") {
+        return {
+          relationshipType: null,
+          childDoc: null,
+        };
+      }
+      const [relationshipType, childDoc] = path.split("/");
+      return {
+        relationshipType: (relationshipType ?? null) as RelationshipType | null,
+        childDoc: (childDoc ?? null) as DocumentId | null,
+      };
+    }),
+  );
+
+function RouteComponent() {
+  const { documentId, _splat } = Route.useParams();
+
+  const { relationshipType, childDoc } = documentParams.parse(_splat);
+
+  return (
+    <DocumentLoader documentId={documentId as DocumentId}>
+      <DocumentView
+        documentId={documentId as DocumentId}
+        relationshipType={relationshipType}
+      />
+    </DocumentLoader>
+  );
+}