feat(dashboard): merge Analytics into Dashboard, remove Kanban Board

Closes issue #5 (Dashboard | Update menu & page):
- Analytics content (heatmap, sparkline, token/cost/workflow/productivity
  charts) moves into a new "Analytics" tab on the Dashboard page, alongside
  the existing Monitor/Health tabs. The standalone Analytics page, its
  /analytics route, and its sidebar menu entry are removed.
- The Kanban Board page, its /kanban route, and its sidebar menu entry are
  removed entirely (page content deleted, not just hidden).
- Updated ARCHITECTURE.md, README.md, client/README.md, docs/API.md, and
  the affected client tests/snapshots to match.

client/src/components/DocumentTitle.tsx

@@ -24,12 +24,8 @@ export function DocumentTitle() {
     title = `${t("sessions")} · ${sessionId.slice(0, 8)}`;
   } else if (path.startsWith("/sessions")) {
     title = t("sessions");
-  } else if (path.startsWith("/kanban")) {
-    title = t("agentBoard");
   } else if (path.startsWith("/activity")) {
     title = t("activityFeed");
-  } else if (path.startsWith("/analytics")) {
-    title = t("analytics");
   } else if (path.startsWith("/workflows")) {
     title = t("workflows");
   } else if (path.startsWith("/cc-config")) {

client/src/components/Sidebar.tsx

@@ -54,7 +54,6 @@ import { NavLink } from "react-router-dom";
 import { useTranslation } from "react-i18next";
 import {
   LayoutDashboard,
-  Columns3,
   FolderOpen,
   Activity,
   BarChart3,
@@ -89,10 +88,8 @@ function isUpdatePayload(x: unknown): x is UpdateStatusPayload {
 
 const NAV_KEYS = [
   { to: "/", icon: LayoutDashboard, key: "nav:dashboard" },
-  { to: "/kanban", icon: Columns3, key: "nav:agentBoard" },
   { to: "/sessions", icon: FolderOpen, key: "nav:sessions" },
   { to: "/activity", icon: Activity, key: "nav:activityFeed" },
-  { to: "/analytics", icon: BarChart3, key: "nav:analytics" },
   { to: "/workflows", icon: Workflow, key: "nav:workflows" },
   { to: "/cc-config", icon: Boxes, key: "nav:ccConfig" },
   { to: "/run", icon: Play, key: "nav:workspace" },

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

@@ -32,7 +32,6 @@ describe("Sidebar", () => {
   it("should render all navigation links", () => {
     renderSidebar(true);
     expect(screen.getByText("Dashboard")).toBeInTheDocument();
-    expect(screen.getByText("Kanban Board")).toBeInTheDocument();
     expect(screen.getByText("Sessions")).toBeInTheDocument();
     expect(screen.getByText("Activity Feed")).toBeInTheDocument();
   });
@@ -60,7 +59,6 @@ describe("Sidebar", () => {
     const links = screen.getAllByRole("link");
     const hrefs = links.map((link) => link.getAttribute("href"));
     expect(hrefs).toContain("/");
-    expect(hrefs).toContain("/kanban");
     expect(hrefs).toContain("/sessions");
     expect(hrefs).toContain("/activity");
   });
@@ -82,7 +80,6 @@ describe("Sidebar", () => {
 
     await waitFor(() => {
       expect(screen.getByText("Tổng quan")).toBeInTheDocument();
-      expect(screen.getByText("Bảng Kanban")).toBeInTheDocument();
     });
   });