[bug]: CommitSig deficiency causes HTLCs insufficiently populated on node restart

[dstadulis]

Background

[incomplete background]

1. In the scenario where one nodes hangs during of path finding,
2. The data which lnd CommitSig handles ?results in a deficient state
3. Which results in downstream uses of lnd (tapd in this case) where HT sigs are blank

Initial CommitSig deficiency

lnd/lnwallet/channel.go

Lines 4096 to 4108 in dcd921a

	// If we signed this state, then we'll accumulate
	// another update to send over.
	case err == nil:
	commitSig := &lnwire.CommitSig{
	ChanID: lnwire.NewChanIDFromOutPoint(
	lc.channelState.FundingOutpoint,
	),
	CommitSig: newCommit.CommitSig,
	HtlcSigs: newCommit.HtlcSigs,
	PartialSig: newCommit.PartialSig,
	}
	updates = append(updates, commitSig)

This should be set:

lnd/lnwallet/channel.go

Line 4745 in 1b353b0

AuxSigBlob: commitDiff.CommitSig.ExtraData,

TODO

• Assess if these gaps could causes UnpackSigs to fail:
  https://github.com/lightninglabs/taproot-assets/blob/8eb6c5345f77d07b07ca9fbb5a76943678049eff/tapchannel/aux_leaf_signer.go#L147

[Roasbeef]

Fixed by #9032