[bug]: failed to send payments in `zero_conf-channel_policy_update_public_zero_conf`

[yyforyongyu]

Found from this build,

--- FAIL: TestLightningNetworkDaemon/tranche01/48-of-301/bitcoind/zero_conf-channel_policy_update_public_zero_conf (151.80s)
        harness_node.go:403: Starting node (name=Eve) with PID=18006
        harness_node.go:403: Starting node (name=Carol) with PID=18306
        harness_node.go:403: Starting node (name=Dave) with PID=18496
        harness_assertion.go:1087: 
            	Error Trace:	/home/runner/work/lnd/lnd/lntest/harness_assertion.go:1087
            	            				/home/runner/work/lnd/lnd/lntest/harness_assertion.go:1040
            	            				/home/runner/work/lnd/lnd/lntest/harness.go:1588
            	            				/home/runner/work/lnd/lnd/lntest/harness.go:1601
            	            				/home/runner/work/lnd/lnd/itest/lnd_zero_conf_test.go:673
            	            				/home/runner/work/lnd/lnd/itest/lnd_zero_conf_test.go:65
            	            				/home/runner/work/lnd/lnd/lntest/harness.go:303
            	            				/home/runner/work/lnd/lnd/itest/lnd_test.go:130
            	Error:      	Received unexpected error:
            	            	received error from payment stream: EOF
            	Test:       	TestLightningNetworkDaemon/tranche01/48-of-301/bitcoind/zero_conf-channel_policy_update_public_zero_conf
            	Messages:   	timeout while waiting payment
        harness.go:381: finished test: zero_conf-channel_policy_update_public_zero_conf, start height=574, end height=588, mined blocks=14
        harness.go:340: test failed, skipped cleanup
    lnd_test.go:138: Failure time: 2025-06-04 15:32:32.374

Eve tried to send a payment to Dave via Carol, but Carol cannot find the channel between her and Dave, causing the payment to fail,

2025-06-04 15:31:01.819 [DBG] HSWC link.go:4115: ChannelLink([ChanPoint: Eve=>Carol]): forwarding 1 packets to switch: replay=false
2025-06-04 15:31:01.822 [DBG] HSWC switch.go:2253: Querying outgoing link using chanID=583:1:0, aliasID=false
2025-06-04 15:31:01.822 [DBG] HSWC switch.go:2869: unable to find link with destination 583:1:0
2025-06-04 15:31:01.822 [ERR] HSWC switch.go:1238: UnknownNextPeer
2025-06-04 15:31:01.822 [ERR] HSWC switch.go:840: Unhandled error while reforwarding htlc settle/fail over htlcswitch: UnknownNextPeer
2025-06-04 15:31:01.822 [DBG] HSWC link.go:1926: ChannelLink([ChanPoint: Eve=>Carol]): queueing removal of FAIL closed circuit: (Chan ID=577:1:0, HTLC ID=0)->(Chan ID=583:1:0, HTLC ID=0)

It's like a bug in zeroconf or channel policy update, causing the channel to not be found here,

lnd/htlcswitch/switch.go

Lines 2285 to 2306 in 4a7cd00

	// The outgoingChanID is a confirmed SCID. Attempt to fetch the base
	// SCID from baseIndex.
	baseScid, ok := s.baseIndex[chanID]
	if !ok {
	// outgoingChanID is not a key in base index meaning this
	// channel did not have the option-scid-alias feature bit
	// negotiated. We'll fetch the link and return it.
	link, ok := s.forwardingIndex[chanID]
	if !ok {
	// The link wasn't found, bail out.
	return nil, ErrChannelLinkNotFound
	}
	return link, nil
	}
	// Fetch the link whose internal SCID is baseScid.
	link, ok := s.forwardingIndex[baseScid]
	if !ok {
	// Link wasn't found, bail out.
	return nil, ErrChannelLinkNotFound
	}