feat: add sparv module and interactive plugin manager

- Add sparv module to config.json (SPARV workflow v1.1)
- Disable essentials module by default
- Add --status to show installation status of all modules
- Add --uninstall to remove installed modules
- Add interactive management mode (install/uninstall via menu)
- Add filesystem-based installation detection
- Support both module numbers and names in selection
- Merge install status instead of overwriting

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Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

config.json

@@ -93,7 +93,7 @@
       ]
     },
     "essentials": {
-      "enabled": true,
+      "enabled": false,
       "description": "Core development commands and utilities",
       "operations": [
         {
@@ -156,6 +156,18 @@
           "description": "Install develop agent prompt"
         }
       ]
+    },
+    "sparv": {
+      "enabled": false,
+      "description": "SPARV workflow (Specify→Plan→Act→Review→Vault) with 10-point gate",
+      "operations": [
+        {
+          "type": "copy_dir",
+          "source": "skills/sparv",
+          "target": "skills/sparv",
+          "description": "Install sparv skill with all scripts and hooks"
+        }
+      ]
     }
   }
 }