installer-rp: delete base resourcepack zip after composing final pack

The RP installer downloads a fresh copy of the base zip into its temp
dir and composes the final pack on top of it. The base zip the main
installer placed in .mc_custom/resourcepacks/ has nothing to do after
that — but it stays in the Minecraft resource-pack list as a second
entry. Delete it after the final zip is written.

Guard against the case where the user set outputPackName equal to the
base filename, which would make base path == final path; in that case
we leave it alone so we don't wipe the file we just wrote.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "minecraft-music-quiz-installer",
-  "version": "0.2.4",
+  "version": "0.2.5",
   "description": "마인크래프트 음악퀴즈 간편설치기 + 관리 사이트",
   "main": "dist/installer/main.js",
   "scripts": {