Implement the 015-add-jscpd-gate feature that adds copy-paste detection to the quality gate using jscpd with a 5% duplication threshold integrated into pnpm check

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

package.json

@@ -3,6 +3,7 @@
 	"packageManager": "pnpm@10.6.0",
 	"devDependencies": {
 		"@biomejs/biome": "2.0.0",
+		"jscpd": "^4.0.8",
 		"knip": "^5.85.0",
 		"lefthook": "^1.11.0",
 		"typescript": "^5.8.0",
@@ -18,6 +19,7 @@
 		"test": "vitest run",
 		"test:watch": "vitest",
 		"knip": "knip",
-		"check": "knip && biome check . && tsc --build && vitest run"
+		"jscpd": "jscpd",
+		"check": "knip && biome check . && tsc --build && vitest run && jscpd"
 	}
 }