[w9-2] Add 90d window, time-window selector, and chart/table toggle (#528)

Backend: widen usage _PeriodType to 24h/7d/30d/90d and add a 90d branch to
_parse_period (daily buckets already cover it). TestParsePeriod pins the
contract per window.

Frontend: UsagePeriod += 90d with a scaleFor helper (replacing 6 inline
ternaries) and 90 daily mock points. One generic SegmentedControl primitive
(reuses Radix Tabs) drives both the metrics time-window selector
(24h/7d/30d/90d) and the per-chart Chart/Table view toggle — one file, two
roles. The Token Usage & Costs tab drops 8 hardcoded '24h' hooks for a
single period state + selector; the stale '(24h)' cost-card parenthetical
goes too. The Performance landing tab gains a TaskStatusChart donut fed by
the status counts already on the page (no new hook). Agent/team bar charts
gain an inline table view.

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

panel/src/components/metrics/__tests__/task-status-chart.test.tsx

@@ -0,0 +1,41 @@
+import { describe, it, expect } from "vitest";
+import { render, screen } from "@testing-library/react";
+import { TaskStatusChart } from "../task-status-chart";
+
+describe("TaskStatusChart", () => {
+  it("renders the card title", () => {
+    render(
+      <TaskStatusChart
+        slices={[
+          { name: "Completed", value: 5 },
+          { name: "Pending", value: 0 },
+        ]}
+      />,
+    );
+    expect(
+      screen.getByText("Task Status Distribution"),
+    ).toBeInTheDocument();
+  });
+
+  it("shows an empty state when every slice is zero", () => {
+    render(
+      <TaskStatusChart
+        slices={[
+          { name: "Pending", value: 0 },
+          { name: "Completed", value: 0 },
+        ]}
+      />,
+    );
+    expect(screen.getByText("No tasks")).toBeInTheDocument();
+  });
+
+  it("does not show the empty state while loading", () => {
+    render(
+      <TaskStatusChart
+        slices={[{ name: "Pending", value: 0 }]}
+        isLoading
+      />,
+    );
+    expect(screen.queryByText("No tasks")).not.toBeInTheDocument();
+  });
+});