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

internal/handlers/api.go

@@ -444,10 +444,11 @@ func (hdlr *Handlers) enqueueNumeric(
 }
 
 // HandleState returns the current session's info and
-// channels.  When called with ?replay=1, it also enqueues
-// synthetic JOIN + TOPIC + NAMES messages for every channel
-// the session belongs to so that a reconnecting client can
-// rebuild its channel tabs from the message stream.
+// channels.  When called with ?initChannelState=1, it also
+// enqueues synthetic JOIN + TOPIC + NAMES messages for every
+// channel the session belongs to so that a reconnecting
+// client can rebuild its channel tabs from the message
+// stream.
 func (hdlr *Handlers) HandleState() http.HandlerFunc {
 	return func(
 		writer http.ResponseWriter,
@@ -475,8 +476,8 @@ func (hdlr *Handlers) HandleState() http.HandlerFunc {
 			return
 		}
 
-		if request.URL.Query().Get("replay") == "1" {
-			hdlr.replayChannelState(
+		if request.URL.Query().Get("initChannelState") == "1" {
+			hdlr.initChannelState(
 				request, clientID, sessionID, nick,
 			)
 		}
@@ -489,12 +490,12 @@ func (hdlr *Handlers) HandleState() http.HandlerFunc {
 	}
 }
 
-// replayChannelState enqueues synthetic JOIN messages and
+// initChannelState enqueues synthetic JOIN messages and
 // join-numerics (TOPIC, NAMES) for every channel the
 // session belongs to.  Messages are enqueued only to the
 // specified client so other clients/sessions are not
 // affected.
-func (hdlr *Handlers) replayChannelState(
+func (hdlr *Handlers) initChannelState(
 	request *http.Request,
 	clientID, sessionID int64,
 	nick string,
@@ -516,7 +517,7 @@ func (hdlr *Handlers) replayChannelState(
 			)
 		if insErr != nil {
 			hdlr.log.Error(
-				"replay: insert JOIN",
+				"initChannelState: insert JOIN",
 				"error", insErr,
 			)