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/fr.json

@@ -98,7 +98,27 @@
     "tokens_used": "Tokens utilises",
     "error_rate": "Taux d'erreur",
     "not_configured": "Non configure",
-    "open_new_tab": "Ouvrir dans un nouvel onglet"
+    "open_new_tab": "Ouvrir dans un nouvel onglet",
+    "agents_status_connected": "Connecte",
+    "agents_status_not_connected": "Non connecte",
+    "agents_config_hint": "Definissez LANGGRAPH_URL dans .env pour vous connecter",
+    "agents_quick_start": "Demarrage rapide",
+    "agents_docs": "Documentation",
+    "agents_docs_desc": "Documentation officielle de LangGraph et guides API.",
+    "agents_getting_started": "Premiers pas",
+    "agents_getting_started_desc": "Tutoriel etape par etape pour creer votre premier agent.",
+    "agents_github": "GitHub",
+    "agents_github_desc": "Code source, issues et contributions de la communaute.",
+    "agents_examples": "Exemples",
+    "agents_examples_desc": "Modeles et projets d'agents prets a l'emploi.",
+    "agents_api_ref": "Reference API",
+    "agents_api_ref_desc": "Documentation Swagger locale pour votre instance LangGraph.",
+    "agents_running_title": "Agents en cours",
+    "agents_none": "Aucun agent enregistre. Deployez un assistant dans LangGraph pour le voir ici.",
+    "agents_col_name": "Nom",
+    "agents_col_id": "ID",
+    "agents_col_description": "Description",
+    "agents_col_status": "Statut"
   },
   "org": {
     "title": "Organisation",