feat(clone-app): add extract-package.sh URL parser with tests

plugins/clone-app/skills/clone-app/scripts/extract-package.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+input="${1:-}"
+if [[ -z "$input" ]]; then
+  echo "ERROR: usage: extract-package.sh <play-url-or-package>" >&2
+  exit 1
+fi
+
+# Case 1: full URL containing id=<package>
+if [[ "$input" =~ id=([a-zA-Z0-9._]+) ]]; then
+  echo "${BASH_REMATCH[1]}"
+  exit 0
+fi
+
+# Case 2: already a bare package (must contain a dot, valid chars only)
+if [[ "$input" =~ ^[a-zA-Z0-9_]+(\.[a-zA-Z0-9_]+)+$ ]]; then
+  echo "$input"
+  exit 0
+fi
+
+echo "ERROR: could not extract package from '$input'" >&2
+exit 1

plugins/clone-app/tests/test-extract-package.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+set -uo pipefail
+SCRIPT="$(dirname "$0")/../skills/clone-app/scripts/extract-package.sh"
+fail=0
+check() {
+  local desc="$1" expected="$2" actual="$3"
+  if [[ "$expected" == "$actual" ]]; then
+    echo "PASS: $desc"
+  else
+    echo "FAIL: $desc — expected '$expected' got '$actual'"; fail=1
+  fi
+}
+
+check "full url" "com.example.app" \
+  "$(bash "$SCRIPT" 'https://play.google.com/store/apps/details?id=com.example.app')"
+check "url with extra params" "com.whatsapp" \
+  "$(bash "$SCRIPT" 'https://play.google.com/store/apps/details?id=com.whatsapp&hl=en&gl=US')"
+check "bare package passthrough" "com.spotify.music" \
+  "$(bash "$SCRIPT" 'com.spotify.music')"
+
+# invalid input → exit 1, empty stdout
+out="$(bash "$SCRIPT" 'not a url' 2>/dev/null)"; rc=$?
+check "invalid exit code" "1" "$rc"
+check "invalid empty stdout" "" "$out"
+
+exit $fail