feat(terminals): reprise de conversation par cellule + fix ordre d'écriture

Permet de recharger la conversation CLI précédente de chaque cellule à la
réouverture du projet, de façon universelle (indépendant du modèle/CLI).

- profil AgentRuntime: bloc déclaratif optionnel `session { assignFlag, resumeFlag }`
- LeafCell: `conversationId` (persistant, distinct du SessionId PTY) + `agentWasRunning`
- runtime: SessionPlan (None/Assign/Resume) + composition pure des args
- LaunchAgent: décide Assign vs Resume, génère l'UUID, remonte l'id assigné
  (persistance par l'appelant via setCellConversation — découplage SRP)
- close: SnapshotRunningAgents fige `agentWasRunning` avant le kill-all
  (statut clot/en cours universel, sans parsing CLI)
- SessionInspector: port optionnel best-effort + adapter ClaudeTranscriptInspector
- popup de reprise par cellule (statut + sujet/tokens si dispo), intercalée
  avant le Resume auto, jamais sur le chemin reattach

fix(terminals): sérialise les écritures PTY (file FIFO par handle) — corrige
les caractères mélangés/accents dus au réordonnancement des invoke Tauri concurrents

fix(layout): l'opération `move` préservait mal les champs du leaf (perdait `agent`)

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

crates/application/tests/layout_usecases.rs

@@ -191,6 +191,8 @@ fn single_leaf(node_id: NodeId) -> LayoutTree {
         id: node_id,
         session: None,
         agent: None,
+        conversation_id: None,
+        agent_was_running: false,
     })
 }
 
@@ -638,6 +640,77 @@ async fn mutate_set_cell_agent_missing_leaf_is_not_found() {
     assert_eq!(err.code(), "NOT_FOUND", "got {err:?}");
 }
 
+// ---------------------------------------------------------------------------
+// SetCellConversation (T4b — persist the assigned CLI conversation id)
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn mutate_set_cell_conversation_persists_id_on_leaf() {
+    let env = mut_env(pid(52)).await;
+    // Record a conversation id on the single root leaf (nid(1)).
+    env.mutate
+        .execute(MutateLayoutInput {
+            project_id: env.project_id,
+            layout_id: None,
+            operation: LayoutOperation::SetCellConversation {
+                target: nid(1),
+                conversation_id: Some("conv-42".to_owned()),
+            },
+        })
+        .await
+        .expect("set_cell_conversation records the id");
+
+    // The id must survive in the persisted JSON, so the next open resumes.
+    let tree_json = active_tree_json(&env.fs);
+    assert_eq!(
+        tree_json["root"]["node"]["conversationId"], "conv-42",
+        "conversation id must be persisted on the leaf"
+    );
+
+    // Now clear it.
+    let out = env
+        .mutate
+        .execute(MutateLayoutInput {
+            project_id: env.project_id,
+            layout_id: None,
+            operation: LayoutOperation::SetCellConversation {
+                target: nid(1),
+                conversation_id: None,
+            },
+        })
+        .await
+        .expect("set_cell_conversation clears the id");
+
+    match &out.layout.root {
+        LayoutNode::Leaf(l) => assert_eq!(l.conversation_id, None, "id must be cleared"),
+        _ => panic!("expected leaf root"),
+    }
+    assert!(
+        active_tree_json(&env.fs)["root"]["node"]
+            .get("conversationId")
+            .is_none(),
+        "cleared id must not be serialised"
+    );
+}
+
+#[tokio::test]
+async fn mutate_set_cell_conversation_missing_leaf_is_not_found() {
+    let env = mut_env(pid(53)).await;
+    let err = env
+        .mutate
+        .execute(MutateLayoutInput {
+            project_id: env.project_id,
+            layout_id: None,
+            operation: LayoutOperation::SetCellConversation {
+                target: nid(404),
+                conversation_id: Some("x".to_owned()),
+            },
+        })
+        .await
+        .expect_err("unknown node rejected");
+    assert_eq!(err.code(), "NOT_FOUND", "got {err:?}");
+}
+
 // ---------------------------------------------------------------------------
 // Named-layout management (#4)
 // ---------------------------------------------------------------------------