merge: 合并小宝预警到 master

# Conflicts:
#	apps/web/lib/xiaobao-risk-trend.test.ts
#	apps/web/lib/xiaobao-risk.ts
#	docs/decisions.md

apps/web/lib/xiaobao-risk-trend.test.ts

@@ -3,7 +3,7 @@ import assert from 'node:assert/strict';
 
 import type { Bug } from './bug';
 import { calcXiaobaoVersionRisk } from './xiaobao-risk';
-import { buildRiskSignature, summarizeRiskTrend } from './xiaobao-risk-trend';
+import { buildRiskSignature, findLatestDailySnapshot, shouldSaveRiskSnapshot, summarizeRiskTrend } from './xiaobao-risk-trend';
 import type { XiaobaoRiskSnapshot } from './xiaobao-risk-trend';
 
 function snapshot(patch: Partial<XiaobaoRiskSnapshot>): XiaobaoRiskSnapshot {
@@ -41,6 +41,45 @@ test('buildRiskSignature changes when score and bug counts change', () => {
   assert.notEqual(base, changed);
 });
 
+test('buildRiskSignature changes when critical bug count changes without open bug count change', () => {
+  const base = buildRiskSignature(snapshot({ openBugCount: 2, criticalBugCount: 0 }));
+  const changed = buildRiskSignature(snapshot({ openBugCount: 2, criticalBugCount: 1 }));
+
+  assert.notEqual(base, changed);
+});
+
+test('findLatestDailySnapshot returns latest same-day snapshot for a version', () => {
+  const latest = findLatestDailySnapshot([
+    snapshot({ versionId: 'ver-1', date: '2026-06-29', riskScore: 40, createdAt: '2026-06-29T09:00:00.000Z' }),
+    snapshot({ versionId: 'ver-1', date: '2026-06-29', riskScore: 45, createdAt: '2026-06-29T10:00:00.000Z' }),
+    snapshot({ versionId: 'ver-1', date: '2026-06-28', riskScore: 70, createdAt: '2026-06-28T10:00:00.000Z' }),
+    snapshot({ versionId: 'ver-2', date: '2026-06-29', riskScore: 90, createdAt: '2026-06-29T11:00:00.000Z' }),
+  ], 'ver-1', '2026-06-29');
+
+  assert.equal(latest?.riskScore, 45);
+});
+
+test('shouldSaveRiskSnapshot skips small same-day changes inside throttle window', () => {
+  const previous = snapshot({ date: '2026-06-29', riskScore: 40, createdAt: '2026-06-29T10:00:00.000Z' });
+  const current = snapshot({ date: '2026-06-29', riskScore: 43, createdAt: '2026-06-29T10:03:00.000Z' });
+
+  assert.equal(shouldSaveRiskSnapshot(current, previous, new Date('2026-06-29T10:03:00.000Z')), false);
+});
+
+test('shouldSaveRiskSnapshot saves material signal changes immediately', () => {
+  const previous = snapshot({ date: '2026-06-29', riskScore: 40, criticalBugCount: 0, createdAt: '2026-06-29T10:00:00.000Z' });
+  const current = snapshot({ date: '2026-06-29', riskScore: 41, criticalBugCount: 1, createdAt: '2026-06-29T10:02:00.000Z' });
+
+  assert.equal(shouldSaveRiskSnapshot(current, previous, new Date('2026-06-29T10:02:00.000Z')), true);
+});
+
+test('shouldSaveRiskSnapshot saves minor signature changes after throttle window', () => {
+  const previous = snapshot({ date: '2026-06-29', riskScore: 40, createdAt: '2026-06-29T10:00:00.000Z' });
+  const current = snapshot({ date: '2026-06-29', riskScore: 43, createdAt: '2026-06-29T10:12:00.000Z' });
+
+  assert.equal(shouldSaveRiskSnapshot(current, previous, new Date('2026-06-29T10:12:00.000Z')), true);
+});
+
 test('calcXiaobaoVersionRisk uses all open bugs in the current trend snapshot signature', () => {
   const now = new Date('2026-07-02T01:00:00.000Z');
   const risk = calcXiaobaoVersionRisk({
@@ -59,19 +98,10 @@ test('calcXiaobaoVersionRisk uses all open bugs in the current trend snapshot si
 
   assert.equal(risk.signals.openBugCount, 1);
   assert.equal(risk.signals.criticalBugCount, 0);
-  assert.equal(currentSignature, buildRiskSignature({
-    versionId: risk.versionId,
-    date: now.toISOString().slice(0, 10),
-    riskScore: risk.riskScore,
-    riskLevel: risk.riskLevel,
-    forecastReleaseDate: risk.forecastReleaseDate,
-    openBugCount: 1,
-    failedTestCount: 0,
-    blockedCount: 0,
-    silentRiskCount: 0,
-    confidence: risk.confidence,
-    createdAt: now.toISOString(),
-  }));
+  assert.equal(risk.currentSnapshot.openBugCount, 1);
+  assert.equal(risk.currentSnapshot.criticalBugCount, 0);
+  assert.equal(currentSignature, buildRiskSignature(risk.currentSnapshot));
+  assert.equal(buildRiskSignature(risk.currentSnapshot).split('|')[5], '1');
 });
 
 function bug(patch: Partial<Bug> = {}): Bug {