Add NickServ LOGOUT command

Clears the account (RPL_LOGGEDOUT) and renames the user to a
configurable guest nick (default Guest) via SVSNICK.

src/proto/inspircd.rs

@@ -2,6 +2,7 @@
 // sequence in Network-Links (protocols/inspircd.py); mode/burst details get
 // firmed up against a live insp4 uplink.
 use super::{NetAction, NetEvent, Protocol};
+use std::time::{SystemTime, UNIX_EPOCH};
 
 pub struct InspIrcd {
     sid: String,
@@ -163,6 +164,12 @@ impl Protocol for InspIrcd {
             NetAction::Metadata { target, key, value } => {
                 vec![self.from_us(format!("METADATA {} {} :{}", target, key, value))]
             }
+            // SVSNICK <uid> <newnick> <nickts> — the new nick takes the current
+            // time as its TS so it wins any collision resolution.
+            NetAction::ForceNick { uid, nick } => {
+                let now = SystemTime::now().duration_since(UNIX_EPOCH).map(|d| d.as_secs()).unwrap_or(self.ts);
+                vec![self.from_us(format!("SVSNICK {} {} {}", uid, nick, now))]
+            }
             NetAction::Raw(s) => vec![s.clone()],
             // Internal: the link layer handles this before serialization.
             NetAction::DeferRegister { .. } => vec![],

src/proto/mod.rs

@@ -34,6 +34,9 @@ pub enum NetAction {
     // Publish network state to the uplink: target "*" is server-global (e.g. the
     // advertised SASL mechanism list), otherwise a user uid (e.g. their account).
     Metadata { target: String, key: String, value: String },
+    // Force a user's nick (SVSNICK), e.g. renaming to a guest nick on logout.
+    // The protocol stamps the new nick's timestamp.
+    ForceNick { uid: String, nick: String },
     Raw(String),
     // Internal only, never serialized to the wire: a registration whose password
     // still needs its (expensive) key derivation. The link layer runs the