feat(p8): vue IDE /workspace (arbre + Monaco + diff + terminal)

- backend: garde-fou conflit d'édition par mtime (GET renvoie mtime, PUT refuse en 409 STALE_FILE si baseMtime périmé)
- lib: wt-key (base64url du chemin worktree), diff-parse (parseur pur du diff unifié → hunks)
- composables: useMonaco (import dynamique → chunk isolé), useWorkspaceLayout (largeurs/panneau persistés)
- components/workspace: GitStatusBadge, FileTree+FileTreeNode (lazy fs/list includeFiles), ChangedFilesPanel, DiffViewer (coloration +/-), MonacoEditor (Ctrl+S + bannière conflit reload/overwrite)
- views/WorkspaceView: 3 colonnes desktop redimensionnables + SegmentedControl mobile, header live (GitStatusBadge), watchWorktree → refresh diff/changements, terminal de la session corrélée
- router meta 'ide' + route /workspace/:repoId/:wt ; App.vue plein écran sans AppShell ; WorktreeCard bouton « Ouvrir l'IDE »
- deps: monaco-editor (lazy, vendor-monaco isolé, 0 impact bundle initial) ; vite manualChunks
- i18n EN+FR (workspace/editor/diff/git) ; tests diff-parse + wt-key ; acceptance-p8.mjs (mtime/409 + diff)

packages/web/src/router/index.ts

@@ -2,10 +2,11 @@ import { createRouter, createWebHistory } from 'vue-router';
 import { useAuthStore } from '../stores/auth';
 
 // Type du layout choisi par App.vue : 'bare' (login, sans coquille),
-// 'shell' (sidebar + contenu centré), 'fullbleed' (terminal plein écran dans la coquille).
+// 'shell' (sidebar + contenu centré), 'fullbleed' (terminal plein écran dans la coquille),
+// 'ide' (vue Workspace plein écran SANS coquille — gère son propre layout 3 panneaux).
 declare module 'vue-router' {
   interface RouteMeta {
-    layout?: 'bare' | 'shell' | 'fullbleed';
+    layout?: 'bare' | 'shell' | 'fullbleed' | 'ide';
   }
 }
 
@@ -16,6 +17,7 @@ export const router = createRouter({
     { path: '/', name: 'dashboard', component: () => import('../views/DashboardView.vue'), meta: { layout: 'shell' } },
     { path: '/sessions', name: 'sessions', component: () => import('../views/SessionsListView.vue'), meta: { layout: 'shell' } },
     { path: '/sessions/:id', name: 'session', component: () => import('../views/SessionView.vue'), meta: { layout: 'fullbleed' } },
+    { path: '/workspace/:repoId/:wt', name: 'workspace', component: () => import('../views/WorkspaceView.vue'), meta: { layout: 'ide' } },
     { path: '/groups', name: 'groups', component: () => import('../views/GroupsListView.vue'), meta: { layout: 'shell' } },
     { path: '/groups/:id', name: 'group', component: () => import('../views/GroupView.vue'), meta: { layout: 'shell' } },
     { path: '/settings', name: 'settings', component: () => import('../views/SettingsView.vue'), meta: { layout: 'shell' } },