Make the relay acknowledge all received commands

To that effect, bump liberty and the xC relay protocol version.
Relay events have been reordered to improve forward compatibility.

Also prevent use-after-free when serialization fails.

xP now slightly throttles activity notifications,
and indicates when there are unacknowledged commands.

xP/public/xP.js

@@ -1,4 +1,4 @@
-// Copyright (c) 2022 - 2024, Přemysl Eric Janouch <p@janouch.name>
+// Copyright (c) 2022 - 2025, Přemysl Eric Janouch <p@janouch.name>
 // SPDX-License-Identifier: 0BSD
 import * as Relay from './proto.js'
 
@@ -67,18 +67,19 @@ class RelayRPC extends EventTarget {
 
 	_processOne(message) {
 		let e = message.data
+		let p
 		switch (e.event) {
 		case Relay.Event.Error:
-			if (this.promised[e.commandSeq] !== undefined)
-				this.promised[e.commandSeq].reject(e.error)
-			else
+			if ((p = this.promised[e.commandSeq]) === undefined)
 				console.error(`Unawaited error: ${e.error}`)
+			else if (p !== true)
+				p.reject(e.error)
 			break
 		case Relay.Event.Response:
-			if (this.promised[e.commandSeq] !== undefined)
-				this.promised[e.commandSeq].resolve(e.data)
-			else
+			if ((p = this.promised[e.commandSeq]) === undefined)
 				console.error("Unawaited response")
+			else if (p !== true)
+				p.resolve(e.data)
 			break
 		default:
 			e.eventSeq = message.eventSeq
@@ -95,6 +96,13 @@ class RelayRPC extends EventTarget {
 			this.promised[seq].reject("No response")
 			delete this.promised[seq]
 		}
+		m.redraw()
+	}
+
+	get busy() {
+		for (const seq in this.promised)
+			return true
+		return false
 	}
 
 	send(params) {
@@ -110,6 +118,9 @@ class RelayRPC extends EventTarget {
 
 		this.ws.send(JSON.stringify({commandSeq: seq, data: params}))
 
+		this.promised[seq] = true
+		m.redraw()
+
 		// Automagically detect if we want a result.
 		let data = undefined
 		const promise = new Promise(
@@ -191,6 +202,17 @@ let bufferAutoscroll = true
 
 let servers = new Map()
 
+let lastActive = undefined
+
+function notifyActive() {
+	// Reduce unnecessary traffic.
+	const now = Date.now()
+	if (lastActive === undefined || (now - lastActive >= 5000)) {
+		lastActive = now
+		rpc.send({command: 'Active'})
+	}
+}
+
 function bufferResetStats(b) {
 	b.newMessages = 0
 	b.newUnimportantMessages = 0
@@ -998,7 +1020,7 @@ let Input = {
 
 	onKeyDown: event => {
 		// TODO: And perhaps on other actions, too.
-		rpc.send({command: 'Active'})
+		notifyActive()
 
 		let b = buffers.get(bufferCurrent)
 		if (b === undefined || event.isComposing)
@@ -1103,7 +1125,13 @@ let Main = {
 
 		return m('.xP', {}, [
 			overlay,
-			m('.title', {}, [m('b', {}, `xP`), m(Topic)]),
+			m('.title', {}, [
+				m('span', [
+					rpc.busy ? '⋯ ' : undefined,
+					m('b', {}, `xP`),
+				]),
+				m(Topic),
+			]),
 			m('.middle', {}, [m(BufferList), m(BufferContainer)]),
 			m(Status),
 			m('.input', {}, [m(Prompt), m(Input)]),