refactor(doorbell-touch): extract lockfile logic to shared script

scripts/lockfile.sh

@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+# Lockfile helper for doorbell build harness
+# Source this from mise tasks
+
+LOCKFILE="/tmp/doorbell-${BOARD:-esp32-32e-4}.lock"
+
+acquire_lock() {
+    if [ -f "$LOCKFILE" ]; then
+        OLD_PID=$(cat "$LOCKFILE" 2>/dev/null)
+        if [ -n "$OLD_PID" ] && kill -0 "$OLD_PID" 2>/dev/null; then
+            if [ "${FORCE:-}" = "1" ]; then
+                echo "Force: Killing existing process (PID: $OLD_PID)..."
+                kill "$OLD_PID" 2>/dev/null
+                sleep 1
+                kill -9 "$OLD_PID" 2>/dev/null
+                echo "Killed PID $OLD_PID"
+            else
+                echo "Error: Another instance is running (PID: $OLD_PID)"
+                echo "Kill with: mise run kill BOARD=$BOARD"
+                echo "Or force with: FORCE=1 mise run $TASK_NAME BOARD=$BOARD"
+                return 1
+            fi
+        else
+            echo "Stale lockfile found, removing..."
+            rm -f "$LOCKFILE"
+        fi
+    fi
+    trap 'rm -f "$LOCKFILE"' EXIT
+    echo "$$" > "$LOCKFILE"
+    echo "Acquired lock: $LOCKFILE (PID: $$)"
+    return 0
+}
+
+release_lock() {
+    rm -f "$LOCKFILE"
+}
+
+kill_locked() {
+    if [ ! -f "$LOCKFILE" ]; then
+        echo "No lockfile found: $LOCKFILE"
+        return 1
+    fi
+
+    OLD_PID=$(cat "$LOCKFILE" 2>/dev/null)
+    if [ -z "$OLD_PID" ]; then
+        echo "Lockfile is empty, removing..."
+        rm -f "$LOCKFILE"
+        return 0
+    fi
+
+    if kill -0 "$OLD_PID" 2>/dev/null; then
+        echo "Killing PID $OLD_PID..."
+        kill "$OLD_PID" 2>/dev/null
+        sleep 1
+        if kill -0 "$OLD_PID" 2>/dev/null; then
+            echo "Force killing PID $OLD_PID..."
+            kill -9 "$OLD_PID" 2>/dev/null
+        fi
+        echo "Killed PID $OLD_PID"
+    else
+        echo "Process $OLD_PID not running (stale lockfile)"
+    fi
+    rm -f "$LOCKFILE"
+    echo "Lockfile removed"
+}