fix(#3029): remove redundant hooks declaration from plugin manifest (#3113)

* fix(#3029): remove redundant hooks declaration from plugin manifest

.claude-plugin/plugin.json declared "hooks": "./hooks/hooks.json"
explicitly. Claude Code already auto-loads hooks/hooks.json by default,
so the explicit declaration caused a duplicate-rejection that silently
disabled every hook the plugin ships — security guards, monitors,
injection scanners. The failure had no visible signal in normal use.

Removed the redundant hooks field. Updated the manifest test to assert
ABSENCE of the field and that the auto-loaded file still exists on disk.

* chore(#3029): backfill changeset PR number 3113

---------

Co-authored-by: sim <sim@local>

.claude-plugin/plugin.json

@@ -19,6 +19,5 @@
     "gsd"
   ],
   "commands": "./commands/gsd/",
-  "skills": "./skills/",
-  "hooks": "./hooks/hooks.json"
+  "skills": "./skills/"
 }