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)

package-lock.json

@@ -3886,6 +3886,12 @@
         "url": "https://github.com/fb55/domhandler?sponsor=1"
       }
     },
+    "node_modules/dompurify": {
+      "version": "3.1.7",
+      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.1.7.tgz",
+      "integrity": "sha512-VaTstWtsneJY8xzy7DekmYWEOZcmzIe3Qb3zPd4STve1OBTa+e+WmS1ITQec1fZYXI3HCsOZZiSMpG6oxoWMWQ==",
+      "license": "(MPL-2.0 OR Apache-2.0)"
+    },
     "node_modules/domutils": {
       "version": "3.2.2",
       "resolved": "https://registry.npmjs.org/domutils/-/domutils-3.2.2.tgz",
@@ -5512,6 +5518,18 @@
         "url": "https://github.com/fb55/entities?sponsor=1"
       }
     },
+    "node_modules/marked": {
+      "version": "14.0.0",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-14.0.0.tgz",
+      "integrity": "sha512-uIj4+faQ+MgHgwUW1l2PsPglZLOLOT1uErt06dAPtx2kjteLAkbsd/0FiYg/MGS+i7ZKLb7w2WClxHkzOOuryQ==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 18"
+      }
+    },
     "node_modules/math-intrinsics": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/math-intrinsics/-/math-intrinsics-1.1.0.tgz",
@@ -5664,6 +5682,16 @@
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       "license": "MIT"
     },
+    "node_modules/monaco-editor": {
+      "version": "0.54.0",
+      "resolved": "https://registry.npmjs.org/monaco-editor/-/monaco-editor-0.54.0.tgz",
+      "integrity": "sha512-hx45SEUoLatgWxHKCmlLJH81xBo0uXP4sRkESUpmDQevfi+e7K1VuiSprK6UpQ8u4zOcKNiH0pMvHvlMWA/4cw==",
+      "license": "MIT",
+      "dependencies": {
+        "dompurify": "3.1.7",
+        "marked": "14.0.0"
+      }
+    },
     "node_modules/ms": {
       "version": "2.1.3",
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
@@ -8476,6 +8504,7 @@
         "@xterm/addon-fit": "^0.11.0",
         "@xterm/addon-webgl": "^0.19.0",
         "@xterm/xterm": "^6.0.0",
+        "monaco-editor": "^0.54.0",
         "pinia": "^3.0.4",
         "vue": "^3.5.38",
         "vue-i18n": "^11.4.5",