docs(AGENTS): add instruction for starting dashboard in multiplexer

When the user asks to start dashboard, check if we are inside tmux/screen
and open a new window titled tdash in the current session rather than
spawning a detached session.

AGENTS.md

@@ -130,6 +130,9 @@ cargo build --release
 ./target/release/scicam-dashboard
 ```
 
+**Agent instruction: starting the dashboard**
+If the user says "start dashboard", check whether the current shell is inside a tmux/screen/byobu session (`$TMUX` or `$STY` or `ps -p $$ -o ppid=` chain includes tmux/screen). If so, open a **new window titled `tdash`** in the *current* session instead of spawning a detached session. If not in a multiplexer, create a new tmux session named `scicam-dashboard` as a fallback.
+
 **Key controls:**
 - `↑/↓` `j/k` — Navigate devices
 - `a` — Add device (enter Name + IP)