fix(projects): le viewer de conversation persiste au changement de layout/projet (#172)

Le viewer (CLI custom) se vidait au changement de layout/projet car l'etat viewerConversationId etait reset sur le changement de projet actif. Remplace par un etat viewerConversation {projectId, conversationId} lie a la conversation elle-meme, rendu contre le projectId de la conversation: la conversation persiste tant que la session headless existe, a l'instar de la TUI native.

frontend/src/features/projects/ProjectsView.tsx

@@ -117,6 +117,11 @@ interface PendingConversationOpen {
   conversationId: string;
 }
 
+interface OpenConversationViewer {
+  projectId: string;
+  conversationId: string;
+}
+
 interface PluginMenuRenderBoundaryProps {
   resetKey: string;
   fallbackMenus: MenuBarMenu[];
@@ -234,9 +239,8 @@ export function ProjectsView() {
   // When set, the main area swaps the terminal grid for the read-only
   // conversation viewer (LS7) — pure local UI state, same mechanic as the
   // terminal↔gitGraph swap; **not** a backend layout kind.
-  const [viewerConversationId, setViewerConversationId] = useState<
-    string | null
-  >(null);
+  const [viewerConversation, setViewerConversation] =
+    useState<OpenConversationViewer | null>(null);
   const [pendingConversationOpen, setPendingConversationOpen] =
     useState<PendingConversationOpen | null>(null);
   const [taskToasts, setTaskToasts] = useState<BackgroundTaskToast[]>([]);
@@ -295,13 +299,12 @@ export function ProjectsView() {
   // loading it against the new project's store fails with "not found: layout X".
   useEffect(() => {
     setActiveLayout(null);
-    setViewerConversationId(null);
   }, [active?.id]);
 
   useEffect(() => {
     if (!active || pendingConversationOpen?.projectId !== active.id) return;
     setSettingsSection(null);
-    setViewerConversationId(pendingConversationOpen.conversationId);
+    setViewerConversation(pendingConversationOpen);
     dismissFloating();
     setPendingConversationOpen(null);
   }, [active?.id, pendingConversationOpen]);
@@ -499,10 +502,12 @@ export function ProjectsView() {
     };
   }, [windowGateway]);
 
-  // Opening a conversation viewer takes over the main area — dismiss floating
-  // windows so they don't obscure the viewer (LS7). Docked views stay beside it.
+  // Opening a conversation viewer takes over the project content area — dismiss
+  // floating windows so they don't obscure the viewer (LS7). Docked views and
+  // the layout tabs stay available beside/above it.
   function openConversation(conversationId: string) {
-    setViewerConversationId(conversationId);
+    if (!active) return;
+    setViewerConversation({ projectId: active.id, conversationId });
     dismissFloating();
   }
 
@@ -525,7 +530,6 @@ export function ProjectsView() {
 
     if (projectOpen) vm.activateTab(toast.projectId);
     setSettingsSection(null);
-    setViewerConversationId(null);
     setPlacement("work", "floating");
   }
 
@@ -901,20 +905,20 @@ export function ProjectsView() {
             onSectionChange={setSettingsSection}
             onClose={() => setSettingsSection(null)}
           />
-        ) : active && viewerConversationId ? (
-          <ConversationViewer
-            key={`${active.id}-${viewerConversationId}`}
-            projectId={active.id}
-            conversationId={viewerConversationId}
-            onClose={() => setViewerConversationId(null)}
-          />
         ) : active ? (
           <>
             <LayoutTabs
               projectId={active.id}
               onActiveLayoutChange={setActiveLayout}
             />
-            {activeLayoutKind === "gitGraph" ? (
+            {viewerConversation ? (
+              <ConversationViewer
+                key={`${viewerConversation.projectId}-${viewerConversation.conversationId}`}
+                projectId={viewerConversation.projectId}
+                conversationId={viewerConversation.conversationId}
+                onClose={() => setViewerConversation(null)}
+              />
+            ) : activeLayoutKind === "gitGraph" ? (
               <GitGraphView
                 key={`${active.id}-${activeLayout?.id ?? "default"}-graph`}
                 projectId={active.id}
@@ -933,6 +937,13 @@ export function ProjectsView() {
               />
             )}
           </>
+        ) : viewerConversation ? (
+          <ConversationViewer
+            key={`${viewerConversation.projectId}-${viewerConversation.conversationId}`}
+            projectId={viewerConversation.projectId}
+            conversationId={viewerConversation.conversationId}
+            onClose={() => setViewerConversation(null)}
+          />
         ) : (
           <div className="flex flex-1 justify-center overflow-y-auto p-6">
             <div className="w-full max-w-xl">