liquidity: integrate scriptable autoloop mode

Add scriptable autoloop as a new mode alongside easy autoloop and
threshold rules. This allows users to provide custom Starlark scripts
that have full control over swap decisions.

Key changes:
- scriptable.go: ScriptableManager that evaluates user scripts on
  each tick, builds context from current channel/peer state, and
  converts script decisions to swap suggestions
- parameters.go: Add ScriptableAutoloop, ScriptableScript, and
  ScriptableTickInterval parameters with validation to ensure
  scriptable mode is mutually exclusive with easy autoloop and rules
- liquidity.go: Wire up scriptable manager to the autoloop system
- script_equivalence_test.go: Tests verifying Starlark scripts can
  replicate easy-autoloop behavior plus advanced scenarios

The scriptable mode gives operators fine-grained control with
readable Python-like syntax:

    def autoloop():
        eligible = [c for c in channels if c.active]
        eligible = sorted(eligible, key=lambda c: -c.local_balance)
        if eligible and total_local > 100000:
            return [loop_out(50000, [eligible[0].channel_id])]
        return []
    decisions = autoloop()

Author: sputn1ck

liquidity/liquidity.go

@@ -293,7 +293,15 @@ func (m *Manager) Run(ctx context.Context) error {
 	for {
 		select {
 		case <-m.cfg.AutoloopTicker.Ticks():
-			if m.params.EasyAutoloop {
+			// Check which autoloop mode to use.
+			// Priority: scriptable > easy > threshold rules.
+			if m.params.ScriptableAutoloop {
+				err := m.scriptableAutoLoop(ctx)
+				if err != nil {
+					log.Errorf("scriptable autoloop "+
+						"failed: %v", err)
+				}
+			} else if m.params.EasyAutoloop {
 				err := m.easyAutoLoop(ctx)
 				if err != nil {
 					log.Errorf("easy autoloop failed: %v",

liquidity/parameters.go

@@ -128,6 +128,18 @@ type Parameters struct {
 	// swaps. If set to true, the deadline is set to immediate publication.
 	// If set to false, the deadline is set to 30 minutes.
 	FastSwapPublication bool
+
+	// ScriptableAutoloop enables CEL-based scriptable autoloop mode.
+	// This mode is mutually exclusive with EasyAutoloop and threshold rules.
+	ScriptableAutoloop bool
+
+	// ScriptableScript is the CEL expression to evaluate on each tick.
+	// Required when ScriptableAutoloop is true.
+	ScriptableScript string
+
+	// ScriptableTickInterval overrides the default tick interval for
+	// scriptable mode. Zero means use DefaultAutoloopTicker.
+	ScriptableTickInterval time.Duration
 }
 
 // AssetParams define the asset specific autoloop parameters.
@@ -195,6 +207,27 @@ func (p Parameters) haveRules() bool {
 func (p Parameters) validate(minConfs int32, openChans []lndclient.ChannelInfo,
 	server *Restrictions) error {
 
+	// Check scriptable autoloop constraints first.
+	if p.ScriptableAutoloop {
+		// Scriptable autoloop is mutually exclusive with easy autoloop.
+		if p.EasyAutoloop {
+			return errors.New("scriptable_autoloop and easy_autoloop " +
+				"are mutually exclusive")
+		}
+
+		// Scriptable autoloop is mutually exclusive with rules.
+		if len(p.ChannelRules) > 0 || len(p.PeerRules) > 0 {
+			return errors.New("scriptable_autoloop cannot be used " +
+				"with channel/peer rules")
+		}
+
+		// Script is required when scriptable autoloop is enabled.
+		if p.ScriptableScript == "" {
+			return errors.New("scriptable_script is required when " +
+				"scriptable_autoloop is enabled")
+		}
+	}
+
 	// First, we check that the rules on a per peer and per channel do not
 	// overlap, since this could lead to contractions.
 	for _, channel := range openChans {
@@ -475,8 +508,11 @@ func RpcToParameters(req *clientrpc.LiquidityParameters) (*Parameters,
 		EasyAutoloopTarget: btcutil.Amount(
 			req.EasyAutoloopLocalTargetSat,
 		),
-		AssetAutoloopParams: easyAssetParams,
-		FastSwapPublication: req.FastSwapPublication,
+		AssetAutoloopParams:    easyAssetParams,
+		FastSwapPublication:    req.FastSwapPublication,
+		ScriptableAutoloop:     req.ScriptableAutoloop,
+		ScriptableScript:       req.ScriptableScript,
+		ScriptableTickInterval: time.Duration(req.ScriptableTickIntervalSec) * time.Second,
 	}
 
 	if req.AutoloopBudgetRefreshPeriodSec != 0 {
@@ -617,10 +653,13 @@ func ParametersToRpc(cfg Parameters) (*clientrpc.LiquidityParameters,
 		HtlcConfTarget:             cfg.HtlcConfTarget,
 		EasyAutoloop:               cfg.EasyAutoloop,
 		EasyAutoloopLocalTargetSat: uint64(cfg.EasyAutoloopTarget),
-		Account:                    cfg.Account,
-		AccountAddrType:            addrType,
-		EasyAssetParams:            easyAssetMap,
-		FastSwapPublication:        cfg.FastSwapPublication,
+		Account:                      cfg.Account,
+		AccountAddrType:              addrType,
+		EasyAssetParams:              easyAssetMap,
+		FastSwapPublication:          cfg.FastSwapPublication,
+		ScriptableAutoloop:           cfg.ScriptableAutoloop,
+		ScriptableScript:             cfg.ScriptableScript,
+		ScriptableTickIntervalSec:    uint64(cfg.ScriptableTickInterval / time.Second),
 	}
 	// Set excluded peers for easy autoloop.
 	rpcCfg.EasyAutoloopExcludedPeers = make(