chore(marketplace): register composer and symphony plugins

Both plugins now have .claude-plugin/plugin.json manifests and are
listed in the root marketplace.json so they can be installed via the
plugin marketplace UI alongside council-of-experts and genealogy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -14,6 +14,16 @@
       "name": "genealogy",
       "source": "./genealogy",
       "description": "Genealogy research methodology — GPS evidence evaluation, FAN workflows, research journal, claim promotion, and transcription."
+    },
+    {
+      "name": "composer",
+      "source": "./composer",
+      "description": "Discovery-phase companion that walks a project from \"I want an app that…\" to a tree of stories in the issue tracker. Pairs with symphony."
+    },
+    {
+      "name": "symphony",
+      "source": "./symphony",
+      "description": "Tracker-agnostic orchestrator daemon — polls the issue tracker, dispatches isolated worker agents per issue, reconciles state. Pairs with composer."
     }
   ]
 }