watchtower: prepare infrastructure for production taproot support

This commit adds preparatory infrastructure and TODO markers in the watchtower
justice kit generation for future production taproot channel support. The
changes establish placeholders for channel type detection and script option
selection that will be needed when watchtowers begin handling breach scenarios
for production taproot channels.

The current implementation includes commented code structures that demonstrate
the intended approach for integrating production script options into the
justice transaction generation process. When channel type information becomes
available in the BreachRetribution structure, these placeholders can be
activated to ensure that watchtowers generate justice transactions using the
appropriate script optimization level.

This preparatory work ensures that the watchtower system has a clear path
toward production taproot support while maintaining current functionality
for staging taproot and legacy channels. The TODO comments provide explicit
guidance for future development when watchtower breach handling for production
taproot channels is implemented.

Author: Roasbeef

watchtower/blob/justice_kit.go

@@ -310,9 +310,17 @@ func newTaprootJusticeKit(sweepScript []byte,
 
 	// TODO(roasbeef): aux leaf tower updates needed
 
+	// TODO: Add channel type info to BreachRetribution to determine
+	// whether to use production scripts for final taproot channels.
+	// For now, we default to staging scripts.
+	var scriptOpts []input.TaprootScriptOpt
+	// if chanType.IsTaprootFinal() {
+	//     scriptOpts = append(scriptOpts, input.WithProdScripts())
+	// }
+
 	tree, err := input.NewLocalCommitScriptTree(
 		breachInfo.RemoteDelay, keyRing.ToLocalKey,
-		keyRing.RevocationKey, fn.None[txscript.TapLeaf](),
+		keyRing.RevocationKey, fn.None[txscript.TapLeaf](), scriptOpts...,
 	)
 	if err != nil {
 		return nil, err
@@ -352,8 +360,15 @@ func (t *taprootJusticeKit) ToLocalOutputSpendInfo() (*txscript.PkScript,
 		return nil, nil, err
 	}
 
+	// TODO: Add channel type info to determine whether to use production
+	// scripts for final taproot channels. For now, we default to staging scripts.
+	var scriptOpts []input.TaprootScriptOpt
+	// if chanType.IsTaprootFinal() {
+	//     scriptOpts = append(scriptOpts, input.WithProdScripts())
+	// }
+
 	revokeScript, err := input.TaprootLocalCommitRevokeScript(
-		localDelayedPubKey, revocationPubKey,
+		localDelayedPubKey, revocationPubKey, scriptOpts...,
 	)
 	if err != nil {
 		return nil, nil, err
@@ -419,8 +434,15 @@ func (t *taprootJusticeKit) ToRemoteOutputSpendInfo() (*txscript.PkScript,
 		return nil, nil, 0, err
 	}
 
+	// TODO: Add channel type info to determine whether to use production
+	// scripts for final taproot channels. For now, we default to staging scripts.
+	var scriptOpts []input.TaprootScriptOpt
+	// if chanType.IsTaprootFinal() {
+	//     scriptOpts = append(scriptOpts, input.WithProdScripts())
+	// }
+
 	scriptTree, err := input.NewRemoteCommitScriptTree(
-		toRemotePk, fn.None[txscript.TapLeaf](),
+		toRemotePk, fn.None[txscript.TapLeaf](), scriptOpts...,
 	)
 	if err != nil {
 		return nil, nil, 0, err