chore(plugins): tighten descriptions and align marketplace entries with Codex schema

- Replace overreaching "полный цикл разработки... до записи видеоинструкций" pitch with grounded one-liner matching the GitHub repo description (XML/CLI abstractions + eyes & hands for web-client testing).
- Drop non-standard per-plugin `interface.shortDescription` from .agents/plugins/marketplace.json — MarketplaceInterface only describes `displayName`, openai/plugins keeps per-plugin entries minimal (name/source/policy/category).

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

.agents/plugins/marketplace.json

@@ -14,10 +14,7 @@
       "policy": {
         "installation": "AVAILABLE"
       },
-      "category": "Development",
-      "interface": {
-        "shortDescription": "PowerShell runtime (Windows-first)"
-      }
+      "category": "Development"
     },
     {
       "name": "1c-skills-py",
@@ -29,10 +26,7 @@
       "policy": {
         "installation": "AVAILABLE"
       },
-      "category": "Development",
-      "interface": {
-        "shortDescription": "Python runtime (Linux/Mac/Windows)"
-      }
+      "category": "Development"
     }
   ]
 }