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_guild_tresure_test.go

@@ -186,6 +186,26 @@ func TestOperateGuildTresureReport_Claim(t *testing.T) {
 	}
 }
 
+// --- handleMsgMhfAcquireGuildTresureSouvenir tests ---
+
+func TestHandleMsgMhfAcquireGuildTresureSouvenir(t *testing.T) {
+	server := createMockServer()
+	session := createMockSession(1, server)
+
+	handleMsgMhfAcquireGuildTresureSouvenir(session, &mhfpacket.MsgMhfAcquireGuildTresureSouvenir{
+		AckHandle: 1,
+	})
+
+	select {
+	case p := <-session.sendPackets:
+		if len(p.data) == 0 {
+			t.Error("response should have data")
+		}
+	default:
+		t.Error("no response queued")
+	}
+}
+
 // --- handleMsgMhfGetGuildTresureSouvenir tests ---
 
 func TestGetGuildTresureSouvenir_Empty(t *testing.T) {