Handle SIGTERM/SIGINT for clean shutdown, add device wrapper script

sdlamp2 now catches SIGTERM and SIGINT via a sig_atomic_t flag checked
in the main loop, ensuring position and volume are saved before exit.
Previously, a kill signal would terminate instantly without saving.

New tools/rg35xx-wrapper.sh replaces sdlamp2 as the dmenu_ln CMD on
the RG35XX Plus. Skeleton includes placeholders for WiFi hotspot and
power button monitoring (TBD after on-device investigation).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tools/rg35xx-wrapper.sh

@@ -0,0 +1,63 @@
+#!/bin/sh
+#
+# RG35XX Plus wrapper for sdlamp2
+#
+# Launched by dmenu_ln instead of sdlamp2 directly. Handles device-specific
+# concerns that don't belong in the player binary:
+#   1. Start WiFi hotspot (AP mode for SSH access)
+#   2. Launch sdlamp2 as the foreground process
+#   3. Monitor power button and trigger clean shutdown
+#
+# Install: copy to /mnt/vendor/bin/rg35xx-wrapper.sh
+# Config:  set CMD in dmenu_ln to point here instead of sdlamp2 directly
+
+SDLAMP2="/mnt/vendor/bin/sdlamp2"
+AUDIO_DIR="/mnt/sdcard/Music"
+
+# --- WiFi hotspot ---
+# TODO: Investigate how the stock menu starts AP mode.
+# Likely candidates: hostapd, nmcli, or a vendor script in /mnt/vendor/ctrl/.
+# Run these on the device to find out:
+#   grep -r 'hostapd\|hotspot\|ap_mode\|wifi' /mnt/vendor/ctrl/
+#   systemctl list-units | grep -i net
+#   nmcli general status && nmcli connection show
+#
+# Placeholder — uncomment/replace once the mechanism is known:
+# nmcli connection up hotspot 2>/dev/null || true
+
+# --- Power button monitor ---
+# TODO: Investigate power button input device.
+# Run on device:
+#   cat /proc/bus/input/devices   (find the power button event device)
+#   evtest /dev/input/eventN      (confirm KEY_POWER event code)
+#   cat /etc/systemd/logind.conf  (check HandlePowerKey setting)
+#
+# Strategy: read key events from the power button input device in background.
+# When KEY_POWER (code 116) is detected, send SIGTERM to sdlamp2 and poweroff.
+#
+# POWER_EVENT_DEV="/dev/input/eventN"  # TBD: set after investigation
+#
+# monitor_power_button() {
+#   # evtest writes one line per event; filter for KEY_POWER press (value 1)
+#   evtest "$POWER_EVENT_DEV" 2>/dev/null | while read -r line; do
+#     case "$line" in
+#       *"code 116"*"value 1"*)
+#         kill -TERM "$SDLAMP2_PID" 2>/dev/null
+#         sleep 1
+#         poweroff
+#         ;;
+#     esac
+#   done
+# }
+# monitor_power_button &
+# MONITOR_PID=$!
+
+# --- Launch sdlamp2 ---
+"$SDLAMP2" "$AUDIO_DIR"
+SDLAMP2_EXIT=$?
+
+# --- Cleanup ---
+# Kill the power button monitor if it's still running
+# kill "$MONITOR_PID" 2>/dev/null
+
+exit "$SDLAMP2_EXIT"