fix(#108): restreint Code Mode Codex au namespace MCP IdeA et documente les tools au démarrage

Codex Code Mode pouvait appeler n'importe quel outil MCP directement,
contournant la médiation d'approbation. On force
[features.code_mode].direct_only_tool_namespaces = ["mcp__idea"] sur
chaque surface qui écrit le config.toml Codex (permission projector,
lifecycle, migration run-dir, assistant de ticket), et on ajoute
initialize.instructions côté serveur MCP pour orienter Codex vers le
bon outil idea_* dès la connexion, sans dépendre de la recherche
sémantique différée.

QA : domain 283/0, application 126/0 + agent_lifecycle 73/0 +
change_agent_profile 19/0 + ticket_assistant 5/0, infrastructure 339/0
dont mcp_server 37/0, backend 68/0 (7 ignored). Les échecs web-server
observés sur cargo test --workspace (Too many open files, cookies)
sont une contamination de ressources inter-tests ; les deux tests
concernés repassent isolément.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/infrastructure/tests/mcp_server.rs

@@ -1887,6 +1887,35 @@ async fn initialize_answers_minimal_handshake() {
     // Capability for tools is advertised, and the server identifies itself.
     assert!(result["capabilities"]["tools"].is_object());
     assert_eq!(result["serverInfo"]["name"], json!("idea-orchestrator"));
+    let instructions = result["instructions"]
+        .as_str()
+        .expect("initialize should advertise compact instructions");
+    let first_512 = instructions.chars().take(512).collect::<String>();
+    for needle in [
+        "idea_ticket_*",
+        "idea_ask_agent",
+        "idea_ask_agents",
+        "idea_memory_*",
+        "idea_context_*",
+    ] {
+        assert!(
+            first_512.contains(needle),
+            "first 512 chars should route natural intent to {needle}; got {first_512:?}"
+        );
+    }
+    for needle in [
+        "idea_skill_*",
+        "idea_template_*",
+        "idea_workstate_*",
+        "background",
+        "agent lifecycle",
+        "sprint",
+    ] {
+        assert!(
+            instructions.contains(needle),
+            "instructions should cover {needle}; got {instructions:?}"
+        );
+    }
 }
 
 /// Readiness de démarrage (fix race cold-launch, signal MCP) : un `initialize` reçu sur