feat: changes to battery warning

hosts/nb/modules/sway/sway.nix

@@ -37,8 +37,10 @@ let
     capacity=$(cat "$cap_file")
     status=$(cat "$status_file" 2>/dev/null || echo "Unknown")
 
+    stamp="/run/user/$(id -u)/.battery_swaynag_stamp"
+    pidfile="/run/user/$(id -u)/.battery_swaynag_pid"
+
     if [[ "$capacity" -lt 20 && "$status" != "Charging" && "$status" != "Full" ]]; then
-      stamp="/run/user/$(id -u)/.battery_swaynag_stamp"
       now=$(date +%s)
       last=0
       if [[ -f "$stamp" ]]; then
@@ -46,10 +48,27 @@ let
       fi
       # Avoid spamming: at most once every 5 minutes
       if (( now - last >= 300 )); then
+        # Kill previous battery swaynag if still running
+        if [[ -f "$pidfile" ]]; then
+          old_pid=$(cat "$pidfile" 2>/dev/null || echo "")
+          if [[ -n "$old_pid" ]] && kill -0 "$old_pid" 2>/dev/null; then
+            kill "$old_pid" 2>/dev/null || true
+          fi
+        fi
         echo "$now" > "$stamp"
         swaynag -t warning -m "Battery low: ''${capacity}% - plug in the charger." -b "Dismiss" "true" &
+        echo $! > "$pidfile"
         disown || true
       fi
+    else
+      # Charging or battery OK - close any existing warning bar
+      if [[ -f "$pidfile" ]]; then
+        old_pid=$(cat "$pidfile" 2>/dev/null || echo "")
+        if [[ -n "$old_pid" ]] && kill -0 "$old_pid" 2>/dev/null; then
+          kill "$old_pid" 2>/dev/null || true
+        fi
+        rm -f "$pidfile" "$stamp"
+      fi
     fi
   '';