OperServ: MODE override and KICK

Two channel operator tools:

- MODE <#chan> <modes> [params] forces a channel mode change (TS 1, so it
  applies regardless of the current TS). A status-mode target may be given
  as a nick — it's resolved to the uid the ircd's FMODE expects.
- KICK <#chan> <nick> [reason] removes a user, sourced from OperServ and
  attributed to the operator.

Both admin-gated. To resolve status-mode params, channel-mode parameter
arity became one shared helper (chanmode_takes_param + STATUS_MODES in the
api): the ircd module now delegates to it instead of keeping its own copy,
so burst-parsing and MODE-building can never drift.

operserv/src/kick.rs

@@ -0,0 +1,26 @@
+use fedserv_api::{NetView, Priv, Sender, ServiceCtx};
+
+// KICK <#channel> <nick> [reason]: remove a user from a channel, sourced from
+// OperServ so it's clearly a staff action. Admin-only.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+    if !from.privs.has(Priv::Admin) {
+        ctx.notice(me, from.uid, "Access denied — KICK needs the \x02admin\x02 privilege.");
+        return;
+    }
+    let Some(&chan) = args.get(1).filter(|c| c.starts_with('#') || c.starts_with('&')) else {
+        ctx.notice(me, from.uid, "Syntax: KICK <#channel> <nick> [reason]");
+        return;
+    };
+    let Some(&target) = args.get(2) else {
+        ctx.notice(me, from.uid, "Syntax: KICK <#channel> <nick> [reason]");
+        return;
+    };
+    let Some(uid) = net.uid_by_nick(target).map(str::to_string) else {
+        ctx.notice(me, from.uid, format!("There's no \x02{target}\x02 online."));
+        return;
+    };
+    let by = from.account.unwrap_or(from.nick);
+    let reason = if args.len() > 3 { args[3..].join(" ") } else { "Removed by services".to_string() };
+    ctx.kick(me, chan, &uid, &format!("({by}) {reason}"));
+    ctx.notice(me, from.uid, format!("\x02{target}\x02 kicked from \x02{chan}\x02."));
+}