Redefine SplicePrototype to use bit 63 instead of 155

Cherry-picked from lightningdevkit#4387 (98c3cff)

This fixes Eclair compatibility issues where Eclair uses bit 155 for an
incompatible previous splice design, causing deserialization failures.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Fernando Ledesma

lightning-types/src/features.rs

@@ -166,15 +166,15 @@ mod sealed {
 			// Byte 6
 			ZeroConf,
 			// Byte 7
-			Trampoline | SimpleClose | SpliceProduction,
+			Trampoline | SimpleClose | SpliceProduction | SplicePrototype,
 			// Byte 8 - 16
 			,,,,,,,,,
 			// Byte 17
 			AnchorZeroFeeCommitmentsStaging,
 			// Byte 18
 			,
 			// Byte 19
-			HtlcHold | SplicePrototype,
+			HtlcHold,
 		]
 	);
 	define_context!(
@@ -195,15 +195,15 @@ mod sealed {
 			// Byte 6
 			ZeroConf | Keysend,
 			// Byte 7
-			Trampoline | SimpleClose | SpliceProduction,
+			Trampoline | SimpleClose | SpliceProduction | SplicePrototype,
 			// Byte 8 - 16
 			,,,,,,,,,
 			// Byte 17
 			AnchorZeroFeeCommitmentsStaging,
 			// Byte 18
 			,
 			// Byte 19
-			HtlcHold | SplicePrototype,
+			HtlcHold,
 			// Byte 20 - 31
 			,,,,,,,,,,,,
 			// Byte 32
@@ -722,7 +722,7 @@ mod sealed {
 		requires_htlc_hold
 	);
 	define_feature!(
-		155, // Splice prototype feature bit as listed in https://github.com/lightning/bolts/issues/605#issuecomment-877237519.
+		63, // Actually the SpliceProduction feature
 		SplicePrototype,
 		[InitContext, NodeContext],
 		"Feature flags for channel splicing.",
@@ -1441,28 +1441,16 @@ mod tests {
 			// - onion_messages
 			// - option_channel_type | option_scid_alias
 			// - option_zeroconf
-			// - option_simple_close | option_splice
-			assert_eq!(node_features.flags.len(), 20);
+			// - option_simple_close
+			assert_eq!(node_features.flags.len(), 8);
 			assert_eq!(node_features.flags[0], 0b00000001);
 			assert_eq!(node_features.flags[1], 0b01010001);
 			assert_eq!(node_features.flags[2], 0b10001010);
 			assert_eq!(node_features.flags[3], 0b00001010);
 			assert_eq!(node_features.flags[4], 0b10001000);
 			assert_eq!(node_features.flags[5], 0b10100000);
 			assert_eq!(node_features.flags[6], 0b00001000);
-			assert_eq!(node_features.flags[7], 0b00100000);
-			assert_eq!(node_features.flags[8], 0b00000000);
-			assert_eq!(node_features.flags[9], 0b00000000);
-			assert_eq!(node_features.flags[10], 0b00000000);
-			assert_eq!(node_features.flags[11], 0b00000000);
-			assert_eq!(node_features.flags[12], 0b00000000);
-			assert_eq!(node_features.flags[13], 0b00000000);
-			assert_eq!(node_features.flags[14], 0b00000000);
-			assert_eq!(node_features.flags[15], 0b00000000);
-			assert_eq!(node_features.flags[16], 0b00000000);
-			assert_eq!(node_features.flags[17], 0b00000000);
-			assert_eq!(node_features.flags[18], 0b00000000);
-			assert_eq!(node_features.flags[19], 0b00001000);
+			assert_eq!(node_features.flags[7], 0b10100000);
 		}
 
 		// Check that cleared flags are kept blank when converting back: