feat(ui): fold the Workflows page into Dashboard → Analytics → Workflow

The workflow analytics now render under the Analytics tab's Workflow
sub-tab; ?tab= and ?sub= deep-link the Dashboard, /workflows redirects there,
and the sidebar drops its Workflows item.

client/src/components/__tests__/DocumentTitle.test.tsx

@@ -33,7 +33,6 @@ describe("DocumentTitle", () => {
   it("titles the other top-level routes", () => {
     expect(titleFor("/")).toMatch(/^Dashboard · /);
     expect(titleFor("/sessions")).toMatch(/^Sessions · /);
-    expect(titleFor("/workflows")).toMatch(/^Workflows · /);
     expect(titleFor("/settings")).toMatch(/^Settings · /);
   });
 });