feat(developer): replace agents iframe with informational landing and live agent table

LangGraph is API-only with no web UI, so the ToolEmbed iframe pattern
doesn't work. Replace it with an informational landing page featuring a
hero section, connection status indicator, quick-start card grid linking
to docs/GitHub/examples, and a live table of registered agents fetched
from the LangGraph POST /assistants/search endpoint.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/i18n/pt.json

@@ -98,7 +98,27 @@
     "tokens_used": "Tokens Utilizados",
     "error_rate": "Taxa de Erros",
     "not_configured": "Nao configurado",
-    "open_new_tab": "Abrir em novo separador"
+    "open_new_tab": "Abrir em novo separador",
+    "agents_status_connected": "Conectado",
+    "agents_status_not_connected": "Nao conectado",
+    "agents_config_hint": "Defina LANGGRAPH_URL no .env para conectar",
+    "agents_quick_start": "Inicio rapido",
+    "agents_docs": "Documentacao",
+    "agents_docs_desc": "Documentacao oficial do LangGraph e guias de API.",
+    "agents_getting_started": "Primeiros passos",
+    "agents_getting_started_desc": "Tutorial passo a passo para criar o seu primeiro agente.",
+    "agents_github": "GitHub",
+    "agents_github_desc": "Codigo fonte, issues e contribuicoes da comunidade.",
+    "agents_examples": "Exemplos",
+    "agents_examples_desc": "Modelos e projetos de agentes prontos a usar.",
+    "agents_api_ref": "Referencia API",
+    "agents_api_ref_desc": "Documentacao Swagger local para a sua instancia LangGraph.",
+    "agents_running_title": "Agentes em execucao",
+    "agents_none": "Nenhum agente registado. Implemente um assistente no LangGraph para o ver aqui.",
+    "agents_col_name": "Nome",
+    "agents_col_id": "ID",
+    "agents_col_description": "Descricao",
+    "agents_col_status": "Estado"
   },
   "org": {
     "title": "Organizacao",