fix: stt-ptt use pkill for better process management

pkgs/stt-ptt/default.nix

@@ -6,6 +6,7 @@
   wtype,
   libnotify,
   pipewire,
+  procps,
   busybox,
 }: let
   script = writeShellScriptBin "stt-ptt" ''
@@ -15,7 +16,6 @@
     CACHE_DIR="''${XDG_CACHE_HOME:-$HOME/.cache}/stt-ptt"
     MODEL_DIR="''${XDG_DATA_HOME:-$HOME/.local/share}/stt-ptt/models"
     AUDIO="$CACHE_DIR/stt.wav"
-    PID_FILE="$CACHE_DIR/stt.pid"
 
     # Configurable via environment
     STT_MODEL="''${STT_MODEL:-$MODEL_DIR/ggml-large-v3-turbo.bin}"
@@ -26,26 +26,31 @@
     PW_RECORD="${pipewire}/bin/pw-record"
     WHISPER="${whisper-cpp}/bin/whisper-cli"
     WTYPE="${wtype}/bin/wtype"
+    PKILL="${procps}/bin/pkill"
     MKDIR="${busybox}/bin/mkdir"
     RM="${busybox}/bin/rm"
-    CAT="${busybox}/bin/cat"
-    KILL="${busybox}/bin/kill"
     TR="${busybox}/bin/tr"
     SED="${busybox}/bin/sed"
+    SLEEP="${busybox}/bin/sleep"
 
     # Ensure cache directory exists
     "$MKDIR" -p "$CACHE_DIR"
 
+    # Kill any existing pw-record for this audio file (prevents orphan nodes)
+    kill_existing() {
+        "$PKILL" -f "pw-record.*$AUDIO" 2>/dev/null
+        "$SLEEP" 0.1
+    }
+
     case "''${1:-}" in
         start)
-            "$RM" -f "$AUDIO" "$PID_FILE"
+            kill_existing
+            "$RM" -f "$AUDIO"
             "$NOTIFY" -t "$STT_NOTIFY_TIMEOUT" -a "stt-ptt" "Recording..."
             "$PW_RECORD" --rate=16000 --channels=1 "$AUDIO" &
-            echo $! > "$PID_FILE"
             ;;
         stop)
-            [[ -f "$PID_FILE" ]] && "$KILL" "$("$CAT" "$PID_FILE")" 2>/dev/null
-            "$RM" -f "$PID_FILE"
+            kill_existing
 
             if [[ -f "$AUDIO" ]]; then
                 if [[ ! -f "$STT_MODEL" ]]; then