`blip-tap.md` needs updating to match the protocols actually used by tapd

[ZZiigguurraatt]

Using this issue to collect errors and omissions in blip-tap.md that need to be fixed to match what tapd actually does.

For starters, TLV types don't match blip-tap.md. For example, we have

taproot-assets/rfqmsg/records.go

Lines 34 to 44 in 331ac78

	type (
	// HtlcAmountRecordType is a type alias for the TLV type that is used to
	// encode an asset ID and amount list within the custom records of an
	// HTLC record on the wire.
	HtlcAmountRecordType = tlv.TlvType65536
	// HtlcRfqIDType is the type alias for the TLV type that is used to
	// encode an RFQ id within the custom records of an HTLC record on the
	// wire.
	HtlcRfqIDType = tlv.TlvType65538
	)

but these numbers don't match those defined at

https://github.com/Roasbeef/blips/blob/579061b962e0212edf6977fd3138522e43897105/blip-tap.md?plain=1#L335-L371 .

I think we also have an issue here

taproot-assets/tapchannelmsg/records.go

Lines 48 to 79 in 331ac78

	type (
	// HtlcAmountRecordType is a type alias for the TLV type that is used to
	// encode an asset ID and amount list within the custom records of an
	// HTLC record on the wire.
	HtlcAmountRecordType = tlv.TlvType65536
	// HtlcSigsRecordType is a type alias for the TLV type that is used to
	// encode the signatures of an HTLC record on the wire.
	HtlcSigsRecordType = tlv.TlvType65537
	// HtlcRfqIDType is the type alias for the TLV type that is used to
	// encode an RFQ id within the custom records of an HTLC record on the
	// wire.
	HtlcRfqIDType = tlv.TlvType65538
	// BtcKeyShutdownType is the type alias for the TLV type that is used to
	// encode the BTC internal key of the shutdown record on the wire.
	BtcKeyShutdownType = tlv.TlvType65539
	// AssetKeyShutdownType is the type alias for the TLV type that is used
	// to encode the asset internal key of the shutdown record on the wire.
	AssetKeyShutdownType = tlv.TlvType65540
	// ScriptKeysShutdownType is the type alias for the TLV type that is
	// used to encode the script keys of the shutdown record on the wire.
	ScriptKeysShutdownType = tlv.TlvType65541
	// ProofDeliveryAddrShutdownType is the type alias for the TLV type that
	// is used to encode the proof delivery address of the shutdown record
	// on the wire.
	ProofDeliveryAddrShutdownType = tlv.TlvType65542
	)

.

I'm not sure where else in the code TLV values are used that we could have similar problems.

I think it likely makes sense to update blip-tap.md and not the code, but I'm not the one to make that decision. I think we need to fix something though because it is hard to understand the code if values don't match the spec.

[ZZiigguurraatt]

We also don't have any definition in the spec how the universe server used for a proof courier is agreed upon when opening a channel.