Auto-join groups: /g and /gjoin auto-create if group doesn't exist

- Server: /join endpoint creates the group if it doesn't exist
- CLI TUI: /g <name> auto-joins before switching
- Web: /g <name> auto-joins before switching
- No more "group not found" errors — just /g ops and go

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/crates/warzone-client/src/tui/app.rs

@@ -204,6 +204,8 @@ impl App {
         }
         if text.starts_with("/g ") {
             let name = text[3..].trim().to_string();
+            // Auto-join
+            self.group_join(&name, client).await;
             self.add_message(ChatLine {
                 sender: "system".into(),
                 text: format!("Switched to group #{}", name),