feat: implement chat merging and logging in Safew

- Introduced a new function `mergeAndLog` in the Watcher to handle merging Safew chats and logging newly discovered chats.
- Added a test `TestNewSafewChatsSkipsKnownIDs` to ensure that known chat IDs are skipped during the merging process.
- Enhanced the polling mechanism to improve chat management and reduce duplicates.

internal/safew/watcher_test.go

@@ -115,6 +115,18 @@ func TestEnsurePollsInBackground(t *testing.T) {
 	w.Stop()
 }
 
+func TestNewSafewChatsSkipsKnownIDs(t *testing.T) {
+	known := map[string]struct{}{"1": {}}
+	got := newSafewChats(known, []adapter.SafewChat{
+		{ID: "1", Title: "old"},
+		{ID: "2", Title: "测试AI", Type: "group"},
+		{ID: "2", Title: "dup"},
+	})
+	if len(got) != 1 || got[0].ID != "2" || got[0].Title != "测试AI" {
+		t.Fatalf("%#v", got)
+	}
+}
+
 func TestPollConflictIsRetryable(t *testing.T) {
 	err := errors.New("safew getUpdates status 400: BAD_REQUEST: Conflict: terminated by other getUpdates request; make sure that only one bot instance is running")
 	if !isGetUpdatesConflict(err) {