common: fix timeline cache race condition and update logic

The GetTimeline function previously used a strict timestamp comparison
(Created > LastCachedTime) to fetch new events. This caused the bot to
miss events occurring within the same second as the last update.

This change:
- Switches to ID-based deduplication to safely handle same-second events.
- Correctly updates existing timeline items if they are modified.
- Calculates the next 'Since' parameter using the maximum 'Updated'
  timestamp found in the current cache.

This fixes flakiness in integration tests (specifically test_006) where
maintainer rejections were occasionally ignored by the workflow-pr service.

common/gitea_utils.go

@@ -863,9 +863,10 @@ func (gitea *GiteaTransport) GetTimeline(org, repo string, idx int64) ([]*models
 	TimelineCache, IsCached := giteaTimelineCache[prID]
 	var LastCachedTime strfmt.DateTime
 	if IsCached {
-		l := len(TimelineCache.data)
-		if l > 0 {
-			LastCachedTime = TimelineCache.data[0].Updated
+		for _, d := range TimelineCache.data {
+			if time.Time(d.Updated).Compare(time.Time(LastCachedTime)) > 0 {
+				LastCachedTime = d.Updated
+			}
 		}
 
 		// cache data for 5 seconds
@@ -894,14 +895,20 @@ func (gitea *GiteaTransport) GetTimeline(org, repo string, idx int64) ([]*models
 		}
 
 		for _, d := range res.Payload {
-			if d != nil {
-				if time.Time(d.Created).Compare(time.Time(LastCachedTime)) > 0 {
-					// created after last check, so we append here
-					TimelineCache.data = append(TimelineCache.data, d)
-				} else {
-					// we need something updated in the timeline, maybe
+			if d == nil {
+				continue
+			}
+			found := false
+			for i := range TimelineCache.data {
+				if TimelineCache.data[i].ID == d.ID {
+					TimelineCache.data[i] = d
+					found = true
+					break
 				}
 			}
+			if !found {
+				TimelineCache.data = append(TimelineCache.data, d)
+			}
 		}
 
 		if resCount < 10 {

integration/tests/workflow_pr_review_test.py

@@ -139,7 +139,6 @@ index 0000000..e69de29
 
 
 @pytest.mark.t005
-# @pytest.mark.xfail(reason="TBD troubleshoot")
 def test_005_any_maintainer_approval_sufficient(maintainer_env, ownerA_client, ownerBB_client):
     """
     Test scenario:
@@ -201,7 +200,6 @@ index 0000000..e69de29
 
 
 @pytest.mark.t006
-@pytest.mark.xfail(reason="tbd flacky in ci")
 def test_006_maintainer_rejection_removes_other_requests(maintainer_env, ownerA_client, ownerBB_client):
     """
     Test scenario: