fix(orchestrator): la délégation simple vers UX renvoie son Final structuré (#207, QA verte)

Une demande idea_ask_agent vers UX échouait avec « finished without a structured Final response » alors qu'Architect répondait. Deux causes corrigées:

- session/process: un tour CLI terminé en code non nul SANS stdout (ex. erreur 401/auth) renvoyait une sortie vide au lieu du stderr réel; l'orchestrateur concluait alors à un « no Final ». On remonte désormais le stderr effectif (drain sync + async + helper process_exit_message + test dédié).

- orchestrator/service: la branche « ask waiting on background » masquait le premier Final structuré; la réponse synchrone redevient le premier Final (suppression de active_rendezvous_has_background_tasks / mark_rendezvous_task_waiting).

Nettoyage runtime corollaire (#204): arrêt du live runtime stale (PTY + structuré) d'un agent recréé afin que la délégation route vers l'agent courant (LiveSessions, stop_live_agent_runtime_in_project, wiring backend via DeleteAgent::with_runtime_cleanup, lifecycle, workstate cascade).

crates/application/src/agent/lifecycle.rs

@@ -43,7 +43,10 @@ use crate::model_server::{
 };
 use crate::project::project_context_path;
 use crate::skill::{AgentCapability, AssignedSkillResolver, ResolveAgentCapabilities};
-use crate::terminal::{StructuredSessions, TerminalSessions};
+use crate::terminal::{
+    stop_live_agent_runtime_in_project, CloseTerminal, LiveSessions, StructuredSessions,
+    TerminalSessions,
+};
 use crate::workstate::GetLiveStateLean;
 
 /// Directory (relative to `.ideai/`) under which agent contexts are written.
@@ -1033,13 +1036,29 @@ pub struct DeleteAgentInput {
 pub struct DeleteAgent {
     contexts: Arc<dyn AgentContextStore>,
     events: Arc<dyn EventBus>,
+    runtime_cleanup: Option<(Arc<LiveSessions>, Arc<CloseTerminal>)>,
 }
 
 impl DeleteAgent {
     /// Builds the use case.
     #[must_use]
     pub fn new(contexts: Arc<dyn AgentContextStore>, events: Arc<dyn EventBus>) -> Self {
-        Self { contexts, events }
+        Self {
+            contexts,
+            events,
+            runtime_cleanup: None,
+        }
+    }
+
+    /// Wires live-runtime cleanup performed before the manifest entry is deleted.
+    #[must_use]
+    pub fn with_runtime_cleanup(
+        mut self,
+        live: Arc<LiveSessions>,
+        close: Arc<CloseTerminal>,
+    ) -> Self {
+        self.runtime_cleanup = Some((live, close));
+        self
     }
 
     /// Drops the manifest entry for the agent.
@@ -1058,6 +1077,11 @@ impl DeleteAgent {
         if entries.len() == before {
             return Err(AppError::NotFound(format!("agent {}", input.agent_id)));
         }
+        if let Some((live, close)) = &self.runtime_cleanup {
+            let _stopped =
+                stop_live_agent_runtime_in_project(&input.project, input.agent_id, live, close)
+                    .await?;
+        }
         let manifest = AgentManifest::new(manifest.version, entries)
             .map_err(|e| AppError::Invalid(e.to_string()))?;
         self.contexts