feat: add search diagnostics logging and tag cardinality tracking

e2e/search.spec.ts

@@ -1,4 +1,28 @@
-import { test, expect } from '@playwright/test';
+import { test, expect, Page } from '@playwright/test';
+
+const SEARCH_QUEUE_KEY = 'obsiviewer.searchdiag.queue';
+
+async function clearDiagnostics(page: Page): Promise<void> {
+  await page.evaluate(key => {
+    localStorage.removeItem(key);
+  }, SEARCH_QUEUE_KEY);
+}
+
+async function readDiagnostics(page: Page): Promise<any[]> {
+  const raw = await page.evaluate(key => localStorage.getItem(key), SEARCH_QUEUE_KEY);
+  if (!raw) {
+    return [];
+  }
+  try {
+    return JSON.parse(raw);
+  } catch {
+    return [];
+  }
+}
+
+function findStage(events: any[], stage: string): any | undefined {
+  return events.find(event => event?.stage === stage);
+}
 
 test.describe('Search Functionality', () => {
   test.beforeEach(async ({ page }) => {
@@ -69,16 +93,43 @@ test.describe('Search Functionality', () => {
   });
 
   test('should filter by tag', async ({ page }) => {
+    await clearDiagnostics(page);
     const searchInput = page.locator('input[type="text"]').first();
-    
+
     await searchInput.fill('tag:#work');
     await searchInput.press('Enter');
-    
+
     await page.waitForTimeout(1000);
     
     // Should show results with #work tag
     const results = page.locator('.search-result');
     await expect(results.first()).toBeVisible({ timeout: 5000 });
+
+    const events = await readDiagnostics(page);
+    const summary = findStage(events, 'SEARCH_DIAG_SUMMARY');
+    expect(summary).toBeTruthy();
+    expect(summary.data?.counts?.displayed).toBeGreaterThan(0);
+    expect(summary.data?.userVisible?.emptyStateShown).toBe(false);
+  });
+
+  test('should record diagnostics when tag search misses index', async ({ page }) => {
+    await clearDiagnostics(page);
+    const searchInput = page.locator('input[type="text"]').first();
+
+    await searchInput.fill('tag:#home');
+    await searchInput.press('Enter');
+
+    await page.waitForTimeout(500);
+
+    const events = await readDiagnostics(page);
+    const summary = findStage(events, 'SEARCH_DIAG_SUMMARY');
+    expect(summary).toBeTruthy();
+    expect(summary.data?.counts?.displayed ?? 0).toBe(0);
+    expect(summary.data?.userVisible?.emptyStateShown).toBe(true);
+
+    const resultMap = findStage(events, 'SEARCH_DIAG_RESULT_MAP');
+    expect(resultMap).toBeTruthy();
+    expect(resultMap.data?.reasonsEmpty).toEqual(expect.arrayContaining(['tagNotInIndex']));
   });
 
   test('should toggle case sensitivity', async ({ page }) => {