Decode the API's actual fields in neoirc-cli (closes #146)

The CLI read the poll cursor from `lastId` while the server sends
`last_id`, so the cursor stayed at 0 and every poll returned the
whole queue at once. It now reads `last_id`.

/names decodes the member objects the server sends and prints each
nick with `@` for an operator or `+` for a voiced member. /list
prints each channel's name and topic, since the server sends no
member count. StateResponse.Channels decodes channel objects.

/topic with no text prints a usage line and sends nothing, because
the HTTP API has no topic query and a TOPIC without text gets 461.
The help says "Set topic".

The client tests serve the bodies the handlers send, so a wrong JSON
tag in types.go fails a test; another test covers the /names prefixes.

Model: opus-5-5

internal/cli/app.go

@@ -434,16 +434,9 @@ func (a *App) cmdTopic(args string) {
 		return
 	}
 
+	// The HTTP API has no topic query: a TOPIC needs text.
 	if args == "" {
-		err := a.client.SendMessage(&api.Message{ //nolint:exhaustruct
-			Command: irc.CmdTopic,
-			To:      target,
-		})
-		if err != nil {
-			a.ui.AddStatus(fmt.Sprintf(
-				"[red]Topic query failed: %v", err,
-			))
-		}
+		a.ui.AddStatus("[red]Usage: /topic <text>")
 
 		return
 	}
@@ -487,12 +480,32 @@ func (a *App) cmdNames() {
 		return
 	}
 
+	nicks := make([]string, 0, len(members))
+
+	for _, member := range members {
+		nicks = append(nicks, memberPrefix(member)+member.Nick)
+	}
+
 	a.ui.AddLine(target, fmt.Sprintf(
 		"[cyan]*** Members of %s: %s",
-		target, strings.Join(members, " "),
+		target, strings.Join(nicks, " "),
 	))
 }
 
+// memberPrefix returns "@" for an operator, "+" for a voiced
+// member, and "" for anyone else.
+func memberPrefix(member api.Member) string {
+	if member.IsOperator {
+		return "@"
+	}
+
+	if member.IsVoiced {
+		return "+"
+	}
+
+	return ""
+}
+
 func (a *App) cmdList() {
 	a.mu.Lock()
 	connected := a.connected
@@ -517,8 +530,7 @@ func (a *App) cmdList() {
 
 	for _, ch := range channels {
 		a.ui.AddStatus(fmt.Sprintf(
-			"  %s (%d members) %s",
-			ch.Name, ch.Members, ch.Topic,
+			"  %s %s", ch.Name, ch.Topic,
 		))
 	}
 
@@ -676,7 +688,7 @@ func (a *App) cmdHelp() {
 		"  /part [#chan]    — Leave channel",
 		"  /msg <nick> <text> — Send DM",
 		"  /query <nick>   — Open DM window",
-		"  /topic [text]   — View/set topic",
+		"  /topic <text>   — Set topic",
 		"  /names          — List channel members",
 		"  /list           — List channels",
 		"  /who [#channel] — List users in channel",