fix: CLI client types mismatched server response format

- SessionResponse: use 'id' (int64) not 'session_id'/'client_id'
- StateResponse: match actual server response shape
- GetMembers: strip '#' from channel name for URL path
- These bugs prevented the CLI from working correctly with the server

cmd/chat-cli/main.go

@@ -145,7 +145,7 @@ func (a *App) cmdConnect(serverURL string) {
 	a.lastQID = 0
 	a.mu.Unlock()
 
-	a.ui.AddStatus(fmt.Sprintf("[green]Connected! Nick: %s, Session: %s", resp.Nick, resp.SessionID))
+	a.ui.AddStatus(fmt.Sprintf("[green]Connected! Nick: %s, Session: %d", resp.Nick, resp.ID))
 	a.ui.SetStatus(resp.Nick, "", "connected")
 
 	// Start polling.