fix: add marketplace.json and remove duplicate hooks declaration

marketplace.json is required for Claude Code plugin indexing.
hooks/hooks.json is auto-discovered — declaring it in plugin.json
causes a duplicate-load error.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude-plugin/plugin.json

@@ -9,6 +9,5 @@
   "homepage": "https://git.sethpc.xyz/Seth/git.sethpc.xyz-connector",
   "repository": "https://git.sethpc.xyz/Seth/git.sethpc.xyz-connector",
   "license": "MIT",
-  "commands": ["./commands"],
-  "hooks": "./hooks/hooks.json"
+  "commands": ["./commands"]
 }