server monitor: qs-stats stream adds cpu temp + wan throughput

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

hosts/FredOS-Mediaserver.nix

@@ -26,6 +26,35 @@
         export PATH="${pkgs.nvd}/bin:${pkgs.coreutils}/bin:${pkgs.gnugrep}/bin:${pkgs.gnused}/bin:$PATH"
         exec ${pkgs.bash}/bin/bash ${../scripts/record-update.sh} "$@"
       '')
+      # Stats stream for the quickshell server monitor on the desktops:
+      # `ssh mediaserver qs-stats` = top's 2s batch stream, interleaved with
+      # one @STAT line per tick (hottest coretemp across both sockets, WAN
+      # byte rates from eno1). Everything rides one SSH connection.
+      (pkgs.writeShellScriptBin "qs-stats" ''
+        C=${pkgs.coreutils}/bin
+        export LC_ALL=C
+        ${pkgs.procps}/bin/top -b -d 2 -w 512 &
+        trap 'kill $! 2>/dev/null' EXIT
+        prev_rx=""
+        while :; do
+          t=0
+          for h in /sys/class/hwmon/*; do
+            if [ "$($C/cat "$h/name" 2>/dev/null)" = coretemp ]; then
+              for f in "$h"/temp*_input; do
+                v=$($C/cat "$f" 2>/dev/null || echo 0)
+                [ "$v" -gt "$t" ] && t=$v
+              done
+            fi
+          done
+          read -r rx tx < <(${pkgs.gawk}/bin/awk '$1 == "eno1:" {print $2, $10}' /proc/net/dev)
+          if [ -n "$prev_rx" ]; then
+            echo "@STAT temp=$((t / 1000)) rxbps=$(( (rx - prev_rx) / 2 )) txbps=$(( (tx - prev_tx) / 2 ))"
+          fi
+          prev_rx=$rx
+          prev_tx=$tx
+          $C/sleep 2
+        done
+      '')
     ];
 
     # Basic networking