feat: Phase 3 — 视角/perspective presets + URL-driven granularity + doctor privacy

Phase 3 of the UX modernization. Frontend-only role view-presets (D2 — no
backend, no JWT role claim, honestly labeled 视角 not 权限). Three conflict-free lanes.

Role infrastructure (worker-session):
- sessionStore with single swappable getRoleSource() seam (localStorage today,
  one-line swap to /api/auth/me for future RBAC); Role = official|community|doctor|admin
- 视角 switcher in TopNav (replaces hardcoded "admin"); on change persists role +
  navigates to that perspective's default landing
- roleViews.ts: ROLE_LABELS + roleDefaultPath (official→/overview?granularity=district,
  community→/monitoring?granularity=street, doctor→/alerts?view=cluster, admin→/monitoring)
- RoleRedirect index route → current role's default; * fallback unchanged

URL-driven granularity (worker-monitoring):
- granularity (city|district|street) query param is the source of truth; drilldownStore
  DERIVES from it via a one-way effect; deep-linkable + reload-safe
- reconciled the imperative desync — DistrictBreakdown no longer calls
  useDrilldownStore.getState(); MonitoringDashboard owns useSearchParams, writes URL
- granularity-control Segmented (全市/区域/街道); district-rollup testid

Role-aware alerts + privacy (worker-alerts):
- doctor/cluster view: individual alert markers hard-locked off (effective flag is
  single source of truth; toggle not rendered) → aggregated density only; DiseaseFilter
  mounted; privacy invariant testable via hidden patient-point DOM mirror (count=0)
- 官员: 100m grid hidden (grid-layer-wrapper unrendered); admin/community unchanged

Gates: tsc 0 · vitest 75 · e2e 30/30 (incl 10 new P3 tests) · build ok

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/e2e/granularity.spec.ts

@@ -0,0 +1,78 @@
+import { test, expect, Page } from '@playwright/test';
+import { TESTIDS } from '../src/utils/testids';
+
+// 与 user-flows.spec.ts 一致的鉴权策略：注入 token 绕过登录门，并 mock /api/**，
+// 让用例脱离活的后端 hermetic 运行。
+async function seedAuthAndMockApi(page: Page) {
+  await page.addInitScript(() => {
+    localStorage.setItem('cbpoa_token', 'e2e-test-token');
+  });
+  await page.route('/api/**', (route) => {
+    const url = route.request().url();
+    if (url.includes('/history/aggregated')) {
+      route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ aggregations: [], total_records: 0 }) });
+      return;
+    }
+    if (url.includes('/grids')) {
+      route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ type: 'FeatureCollection', features: [] }) });
+      return;
+    }
+    if (url.includes('/streets')) {
+      route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ streets: [] }) });
+      return;
+    }
+    if (url.includes('/cases/districts') || url.includes('/districts')) {
+      route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify([]) });
+      return;
+    }
+    if (url.includes('/cases/trend') || url.includes('/cases')) {
+      route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ data: [], trend: [], total: 0 }) });
+      return;
+    }
+    route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ data: [], items: [], total: 0 }) });
+  });
+}
+
+// 粒度（granularity）以 URL query 参数为真相来源（source of truth）。
+// 监测页通过 useSearchParams 读取它，drilldownStore 单向派生。
+test.describe('monitoring granularity URL source-of-truth', () => {
+  test.beforeEach(async ({ page }) => {
+    await seedAuthAndMockApi(page);
+  });
+
+  test('deep-link granularity=street mounts page and reflects street in control', async ({ page }) => {
+    await page.goto('/monitoring?granularity=street');
+
+    await expect(page.getByTestId(TESTIDS.pageMonitoring)).toBeVisible();
+
+    const control = page.getByTestId(TESTIDS.granularityControl);
+    await expect(control).toBeVisible();
+    // 街道分段为激活态（Segmented 给激活按钮加 bg-primary）。
+    const streetBtn = page.getByTestId(`${TESTIDS.granularityControl}-street`);
+    await expect(streetBtn).toHaveClass(/bg-primary/);
+  });
+
+  test('clicking a granularity control updates the URL granularity param', async ({ page }) => {
+    await page.goto('/monitoring?granularity=street');
+    await expect(page.getByTestId(TESTIDS.pageMonitoring)).toBeVisible();
+
+    // 切到「区域」应把 URL 写为 granularity=district。
+    await page.getByTestId(`${TESTIDS.granularityControl}-district`).click();
+    await expect(page).toHaveURL(/granularity=district/);
+
+    // 切到「全市」应把 URL 写为 granularity=city。
+    await page.getByTestId(`${TESTIDS.granularityControl}-city`).click();
+    await expect(page).toHaveURL(/granularity=city/);
+  });
+
+  test('deep-link granularity=district survives a reload', async ({ page }) => {
+    await page.goto('/monitoring?granularity=district');
+    await expect(page.getByTestId(TESTIDS.pageMonitoring)).toBeVisible();
+    await expect(page).toHaveURL(/granularity=district/);
+
+    await page.reload();
+    await expect(page.getByTestId(TESTIDS.pageMonitoring)).toBeVisible();
+    await expect(page).toHaveURL(/granularity=district/);
+    await expect(page.getByTestId(`${TESTIDS.granularityControl}-district`)).toHaveClass(/bg-primary/);
+  });
+});