bump(box): 20374501 → 15b5c2a5 (#5699)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

.claude-plugin/marketplace.json

@@ -596,7 +596,7 @@
       "source": {
         "source": "url",
         "url": "https://github.com/box/box-for-ai.git",
-        "sha": "20374501fc7323c359bc67779520fbd75c36fc82"
+        "sha": "15b5c2a567f43b0c13b14b33aab964d080a444cd"
       },
       "skills": [
         "./skills/box",