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/README.md

@@ -67,12 +67,10 @@ graph TB
             Layout[Layout Component]
             
             subgraph "Pages"
-                Home[Dashboard]
-                Kanban[KanbanBoard]
+                Home[Dashboard<br/>Monitor / Analytics / Health tabs]
                 Sessions[Sessions]
                 Detail[SessionDetail]
                 Feed[ActivityFeed]
-                Analytics[Analytics]
                 Workflows[Workflows]
                 Settings[Settings]
             end
@@ -100,7 +98,7 @@ graph TB
     end
     
     Router --> Layout
-    Layout --> Home & Kanban & Sessions & Detail & Feed & Analytics & Workflows & Settings
+    Layout --> Home & Sessions & Detail & Feed & Workflows & Settings
     Home & Detail --> AgentCard & StatCard & StatusBadge
     Feed --> EventDetail
     API --> REST
@@ -183,12 +181,10 @@ client/
 │   │   └── workflows/      # D3.js workflow visualization components (12 files)
 │   │
 │   ├── pages/              # Route pages
-│   │   ├── Dashboard.tsx
-│   │   ├── KanbanBoard.tsx
+│   │   ├── Dashboard.tsx      # Monitor / Analytics / Health tabs
 │   │   ├── Sessions.tsx       # Filterable table; shows each session's real name (synced live from the transcript), falls back to the short ID
 │   │   ├── SessionDetail.tsx  # Agent tree + event timeline + Conversation tab (slash-command pills & output, inline rename markers)
 │   │   ├── ActivityFeed.tsx  # Real-time event log; row click expands payload; Session btn navigates
-│   │   ├── Analytics.tsx
 │   │   ├── Workflows.tsx
 │   │   ├── Settings.tsx
 │   │   └── NotFound.tsx
@@ -230,17 +226,15 @@ graph TB
     App[App.tsx<br/>Router + WS + Notifications]
     Layout[Layout.tsx<br/>Sidebar + Outlet]
 
-    Dashboard[Dashboard<br/>Monitor tab: stats + agents + events<br/>Health tab: SystemHealthTab]
-    Kanban[KanbanBoard<br/>4-column agent board]
+    Dashboard[Dashboard<br/>Monitor tab: stats + agents + events<br/>Analytics tab: tokens + heatmap + trends<br/>Health tab: SystemHealthTab]
     Sessions[Sessions<br/>filterable table]
     Detail[SessionDetail<br/>agent hierarchy + timeline]
     Feed[ActivityFeed<br/>streaming event log]
-    Analytics[Analytics<br/>tokens + heatmap + trends]
     Workflows[Workflows<br/>D3.js visualizations]
     Settings[Settings<br/>pricing + notifications + hooks]
 
     App --> Layout
-    Layout --> Dashboard & Kanban & Sessions & Detail & Feed & Analytics & Workflows & Settings
+    Layout --> Dashboard & Sessions & Detail & Feed & Workflows & Settings
 
     Dashboard --> StatCard[StatCard × 6]
     Dashboard --> AgentCard[AgentCard × N]
@@ -450,18 +444,16 @@ useEffect(() => {
 graph TB
     Root["/"]
     Dashboard["/ (Dashboard)"]
-    Kanban["/kanban"]
     Sessions["/sessions"]
     Detail["/sessions/:id"]
     Feed["/activity"]
-    Analytics["/analytics"]
     Workflows["/workflows"]
     CcConfig["/cc-config"]
     Run["/run"]
     Settings["/settings"]
     NF["/* (NotFound)"]
 
-    Root --> Dashboard & Kanban & Sessions & Detail & Feed & Analytics & Workflows & CcConfig & Run & Settings & NF
+    Root --> Dashboard & Sessions & Detail & Feed & Workflows & CcConfig & Run & Settings & NF
 
     style Dashboard fill:#3B82F6
     style Detail fill:#3B82F6
@@ -480,11 +472,9 @@ function App() {
       <Routes>
         <Route path="/" element={<Layout />}>
           <Route index element={<Dashboard />} />
-          <Route path="kanban" element={<KanbanBoard />} />
           <Route path="sessions" element={<Sessions />} />
           <Route path="sessions/:id" element={<SessionDetail />} />
           <Route path="activity" element={<ActivityFeed />} />
-          <Route path="analytics" element={<Analytics />} />
           <Route path="workflows" element={<Workflows />} />
           <Route path="cc-config" element={<CcConfig />} />
           <Route path="run" element={<Run />} />
@@ -883,7 +873,7 @@ test('renders session title and cost', () => {
 ### Snapshot Testing
 
 `pages/__tests__/screens.snapshot.test.tsx` renders **every routed screen**
-(Dashboard, Kanban, Sessions, Session detail, Activity feed, Analytics,
+(Dashboard, Sessions, Session detail, Activity feed,
 Workflows, Claude Config, Run, Settings, Not found) and asserts each against a
 committed snapshot in `pages/__tests__/__snapshots__/`. These are structural
 regression guards — they catch unintended changes to layout, markup, or