feat: add BreadcrumbProvider and e2e test suite

Add BreadcrumbProvider context so pages can override TopBar breadcrumbs
dynamically. Add Playwright e2e tests for dashboard, agents, routes,
exchanges, and admin pages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

e2e/exchanges.spec.ts

@@ -0,0 +1,60 @@
+import { test, expect } from '@playwright/test'
+
+test.describe('Exchange Detail (/exchanges/:id)', () => {
+  test('renders exchange header, timeline, and message panels', async ({ page }) => {
+    await page.goto('/exchanges/E-2026-03-18-00201')
+
+    // Exchange header — use the one NOT in the breadcrumb
+    await expect(page.getByText('E-2026-03-18-00201').nth(1)).toBeVisible()
+
+    // Header stats
+    await expect(page.getByText('Duration').first()).toBeVisible()
+    await expect(page.getByText('Processors').first()).toBeVisible()
+
+    // Processor Timeline section
+    await expect(page.getByText('Processor Timeline').first()).toBeVisible()
+
+    // Timeline/Flow toggle buttons
+    await expect(page.getByRole('button', { name: 'Timeline' })).toBeVisible()
+    await expect(page.getByRole('button', { name: 'Flow' })).toBeVisible()
+
+    // Message IN panel
+    await expect(page.getByText('Message IN')).toBeVisible()
+    await expect(page.getByText('Headers').first()).toBeVisible()
+    await expect(page.getByText('Body').first()).toBeVisible()
+  })
+
+  test('switching between Timeline and Flow view', async ({ page }) => {
+    await page.goto('/exchanges/E-2026-03-18-00201')
+
+    // Default view is timeline (gantt)
+    const timelineBtn = page.getByRole('button', { name: 'Timeline' })
+    const flowBtn = page.getByRole('button', { name: 'Flow' })
+
+    // Switch to Flow view
+    await flowBtn.click()
+
+    // Flow view should render (RouteFlow component)
+    await expect(flowBtn).toHaveClass(/active|Active/)
+
+    // Switch back to Timeline
+    await timelineBtn.click()
+    await expect(timelineBtn).toHaveClass(/active|Active/)
+  })
+
+  test('not-found exchange shows warning', async ({ page }) => {
+    await page.goto('/exchanges/nonexistent-id')
+
+    await expect(page.getByText('not found', { exact: false })).toBeVisible()
+  })
+
+  test('breadcrumb navigation works', async ({ page }) => {
+    await page.goto('/exchanges/E-2026-03-18-00201')
+
+    // Click Applications breadcrumb to go back
+    const appsBreadcrumb = page.getByRole('link', { name: 'Applications' })
+    await appsBreadcrumb.click()
+
+    await expect(page).toHaveURL(/\/apps/)
+  })
+})