rename replay query parameter to initChannelState

Rename ?replay=1 to ?initChannelState=1 across server, SPA, and docs
per review feedback: the parameter initialises fresh channel state
rather than replaying past state.

- Rename replayChannelState() to initChannelState()
- Update query parameter check in HandleState
- Update SPA fetch URL and comments
- Update README documentation and curl examples

web/src/app.jsx

@@ -70,7 +70,7 @@ function LoginScreen({ onLogin }) {
       .catch(() => {});
     const saved = localStorage.getItem("neoirc_token");
     if (saved) {
-      api("/state?replay=1")
+      api("/state?initChannelState=1")
         .then((u) => onLogin(u.nick, true))
         .catch(() => localStorage.removeItem("neoirc_token"));
     }
@@ -335,7 +335,7 @@ function App() {
           if (msg.to) addMessage(msg.to, { ...base, text, system: true });
           if (msg.to && msg.to.startsWith("#")) {
             // Create a tab when the current user joins a channel
-            // (including replayed JOINs on reconnect).
+            // (including initial JOINs on reconnect).
             if (msg.from === nickRef.current) {
               setTabs((prev) => {
                 if (
@@ -656,8 +656,8 @@ function App() {
       if (isResumed) {
         // Request MOTD on resumed sessions (new sessions
         // get it automatically from the server during
-        // creation).  Channel state is replayed by the
-        // server via the message queue (?replay=1), so we
+        // creation).  Channel state is initialised by the
+        // server via the message queue (?initChannelState=1), so we
         // do not need to re-JOIN channels here.
         try {
           await api("/messages", {