refactor(channelserver): consolidate tests into matching source test files

Move ~300 test functions from 21 catch-all files (handlers_core_test.go,
handlers_coverage*_test.go, *_coverage_test.go) into the *_test.go file
matching each handler's source file. This makes tests discoverable by
convention: tests for handlers_guild.go live in handlers_guild_test.go.

New files: handlers_guild_mission_test.go, sys_time_test.go.
No test logic changed — pure file reorganization.

server/channelserver/handlers_rengoku_test.go

@@ -51,3 +51,79 @@ func TestRengokuScoreStruct_DefaultValues(t *testing.T) {
 		t.Errorf("Default Score should be 0, got %d", score.Score)
 	}
 }
+
+func TestHandleMsgMhfGetRengokuRankingRank_ResponseData(t *testing.T) {
+	server := createMockServer()
+	session := createMockSession(1, server)
+
+	pkt := &mhfpacket.MsgMhfGetRengokuRankingRank{
+		AckHandle: 55555,
+	}
+
+	handleMsgMhfGetRengokuRankingRank(session, pkt)
+
+	select {
+	case p := <-session.sendPackets:
+		if len(p.data) == 0 {
+			t.Error("Response packet should have data")
+		}
+	default:
+		t.Error("No response packet queued")
+	}
+}
+
+func TestRengokuScoreStruct_Fields(t *testing.T) {
+	score := RengokuScore{
+		Name:  "Hunter",
+		Score: 99999,
+	}
+
+	if score.Name != "Hunter" {
+		t.Errorf("Name = %s, want Hunter", score.Name)
+	}
+	if score.Score != 99999 {
+		t.Errorf("Score = %d, want 99999", score.Score)
+	}
+}
+
+// TestHandleMsgMhfGetRengokuRankingRank_DifferentAck verifies rengoku ranking
+// works with different ack handles.
+func TestHandleMsgMhfGetRengokuRankingRank_DifferentAck(t *testing.T) {
+	server := createMockServer()
+
+	ackHandles := []uint32{0, 1, 54321, 0xDEADBEEF}
+	for _, ack := range ackHandles {
+		session := createMockSession(1, server)
+		pkt := &mhfpacket.MsgMhfGetRengokuRankingRank{AckHandle: ack}
+
+		handleMsgMhfGetRengokuRankingRank(session, pkt)
+
+		select {
+		case p := <-session.sendPackets:
+			if len(p.data) == 0 {
+				t.Errorf("AckHandle=%d: Response packet should have data", ack)
+			}
+		default:
+			t.Errorf("AckHandle=%d: No response packet queued", ack)
+		}
+	}
+}
+
+// Tests consolidated from handlers_coverage3_test.go
+
+func TestNonTrivialHandlers_RengokuGo(t *testing.T) {
+	server := createMockServer()
+
+	t.Run("handleMsgMhfGetRengokuRankingRank", func(t *testing.T) {
+		session := createMockSession(1, server)
+		handleMsgMhfGetRengokuRankingRank(session, &mhfpacket.MsgMhfGetRengokuRankingRank{AckHandle: 1})
+		select {
+		case p := <-session.sendPackets:
+			if len(p.data) == 0 {
+				t.Error("response should have data")
+			}
+		default:
+			t.Error("no response queued")
+		}
+	})
+}