fix(runtime): stop/restart d'agent visible robuste — kill réel, état stopped, relance froide (#196, QA verte)

Solidifie le cycle stop/restart d'un agent visible en cellule:

- terminal/registry: kill effectif de la TUI native et de la CLI custom, arrêt idempotent du live runtime (PTY + structuré), distinction nette « agent stoppé » vs « pas de session ».

- workstate + lifecycle: projection d'un état runtime explicite « stopped » (AgentRuntimeState: running/stopping/stopped/failedStart), réconcilié avec le live state; traitement des courses « agent not found ».

- relance froide via freshStart: repart de zéro sans réattacher une session morte et recharge la configuration courante de l'agent (y compris changement de modèle).

- contrat projeté côté adapters frontend (ports/domain/normalization/mock) pour la consommation UI future (#197/#198), sans surface UI ici.

Tests QA verts: workstate_actions, orchestrator_service stop_agent, agent_lifecycle (reopen/fresh_start), workstate stopped runtime state, vitest adapter stop_live_agent.

crates/application/src/workstate/actions.rs

@@ -16,7 +16,8 @@ use domain::{AgentId, NodeId, Project, RuntimeAgentKey, SessionId};
 use crate::error::AppError;
 use crate::orchestrator::OrchestratorService;
 use crate::terminal::{
-    stop_live_agent_runtime_in_project, CloseTerminal, LiveSessionKind, LiveSessions,
+    stop_live_agent_runtime_in_project, CloseTerminal, LiveRuntimeState, LiveSessionKind,
+    LiveSessions,
 };
 
 /// Input for [`AttachLiveAgent::execute`].
@@ -115,8 +116,12 @@ pub struct StopLiveAgentOutput {
     pub agent_id: AgentId,
     /// The id of the session that was torn down.
     pub session_id: SessionId,
+    /// Last known layout node hosting the runtime view.
+    pub node_id: NodeId,
     /// Runtime family that owned the session.
     pub kind: LiveSessionKind,
+    /// Runtime lifecycle projection after the stop request.
+    pub runtime_state: LiveRuntimeState,
 }
 
 /// Best-effort stopper for execution resources owned by one live agent turn.
@@ -232,7 +237,26 @@ impl StopLiveAgent {
             .map(|stopped| StopLiveAgentOutput {
                 agent_id: stopped.agent_id,
                 session_id: stopped.session_id,
+                node_id: stopped.node_id,
                 kind: stopped.kind,
+                runtime_state: stopped.state,
+            })
+            .or_else(|| {
+                self.live
+                    .runtime_status_for(project.id, &agent_id)
+                    .filter(|status| {
+                        matches!(
+                            status.state,
+                            LiveRuntimeState::Stopping | LiveRuntimeState::Stopped
+                        )
+                    })
+                    .map(|status| StopLiveAgentOutput {
+                        agent_id: status.agent_id,
+                        session_id: status.session_id,
+                        node_id: status.node_id,
+                        kind: status.kind,
+                        runtime_state: status.state,
+                    })
             })
             .ok_or_else(|| AppError::NotFound(format!("running session for agent {agent_id}")))
     }