fix(ai+editeur): BUG-046 erreur lisible et vault réel pour l'ajout IA au document; BUG-045 fin de la double scrollbar

BUG-046: 'Ajouter du texte au document courant' échouait avec 'Échec de
l'action: [object Object]'. Trois causes corrigées:
- continuation de confirmation sans payload -> second Appliquer POSTait
  sans 'message' (422); le payload d'origine est désormais transmis
- detail 422 FastAPI (tableau d'objets) stringifié tel quel -> nouvelle
  _responseError() qui aplatit en message lisible
- prompt documents/dossier muet sur le vault -> le modèle inventait
  'vault: test' et append_to_file échouait en silence; build_system_prompt
  nomme le vault et enjoint les outils d'écriture de l'utiliser exactement

BUG-045: double barre de défilement dans l'éditeur Editer (fichiers
longs): #editor-body overflow:auto + cm-editor height:100% sous la barre
IA -> corps et scroller CodeMirror défilant tous les deux. Flex column,
seul le scroller défile; override global .cm-scroller retiré. SW v20.

Vérifié: pytest 1038, ruff backend 0, tests frontend AI 84/84,
editor-inline 25/25, validate-imports 38 modules; Playwright sur
l'instance de test (un seul conteneur scrollable) et flux agent complet
append_to_file ok=true sur fichier réel

frontend/js/bookslm.js

@@ -2397,6 +2397,27 @@ class BooksLM {
     return html;
   }
 
+  /**
+   * Build a readable Error from a non-OK /chat or /agent response. BUG-046:
+   * a 422 validation error carries `detail` as an ARRAY of objects (FastAPI),
+   * which `new Error(detail)` stringified to "[object Object]" in the
+   * "Échec de l'action" toast. Flatten arrays / objects into their messages.
+   */
+  async _responseError(resp) {
+    let detail = `HTTP ${resp.status}`;
+    try {
+      const body = await resp.json();
+      const d = body && body.detail;
+      if (typeof d === 'string' && d) detail = d;
+      else if (Array.isArray(d) && d.length) {
+        detail = d.map((item) => (item && (item.msg || item.message)) || JSON.stringify(item)).join(' · ');
+      } else if (d && typeof d === 'object') {
+        detail = d.msg || d.message || JSON.stringify(d);
+      }
+    } catch { /* no json body */ }
+    return new Error(detail);
+  }
+
   async _applyConfirmation(msg) {
     const conf = msg.confirmation;
     if (!conf || conf._applying) return;
@@ -2413,7 +2434,11 @@ class BooksLM {
     const sendBtn = this._panel && this._panel.querySelector('.bookslm-btn-send');
     if (sendBtn) sendBtn.disabled = true;
 
-    const continuation = { role: 'assistant', content: '', sources: [], toolCalls: [], confirmation: null, payload: null };
+    // BUG-046: carry the original request payload over to the continuation.
+    // When an applied tool failed and the model re-proposed a confirmation,
+    // the continuation used to have `payload: null`: the second "Appliquer"
+    // then resumed without `message` → 422 → "[object Object]" toast.
+    const continuation = { role: 'assistant', content: '', sources: [], toolCalls: [], confirmation: null, payload: msg.payload ? { ...msg.payload } : null };
     try {
       let resp = await this._postChat(payload);
       if (resp.status === 401 && AuthManager._authEnabled) {
@@ -2421,9 +2446,7 @@ class BooksLM {
         resp = await this._postChat(payload);
       }
       if (!resp.ok) {
-        let detail = `HTTP ${resp.status}`;
-        try { detail = (await resp.json()).detail || detail; } catch { /* */ }
-        throw new Error(detail);
+        throw await this._responseError(resp);
       }
       // The confirmation is resolved: drop the card and show the continuation.
       msg.confirmation = null;

frontend/style.css

@@ -3003,8 +3003,16 @@ select {
 @keyframes editor-pulse { 0%,100% { opacity: 1; } 50% { opacity: 0.4; } }
 .editor-save-dot.saving { animation: editor-pulse 0.8s infinite; }
 .editor-save-dot.err { color: var(--err); } .editor-save-dot.err .dot { background: var(--err); }
-.editor-body-cm { flex: 1; overflow: auto; }
-.editor-body-cm .cm-editor { height: 100%; }
+/* BUG-045: only the CodeMirror scroller scrolls. #editor-body used to keep
+   overflow:auto AND host a 100%-tall .cm-editor below the AI toolbar row,
+   so the body (toolbar + editor) and the scroller both overflowed → two
+   stacked scrollbars. Flex column: toolbar fixed, editor fills, scroller
+   scrolls. Combined selector on purpose: `.editor-body` (defined later with
+   equal specificity) must not re-introduce overflow-y:auto. */
+.editor-body.editor-body-cm { flex: 1; min-height: 0; overflow: hidden; display: flex; flex-direction: column; }
+.editor-body.editor-body-cm #ai-toolbar-container { flex: 0 0 auto; }
+.editor-body.editor-body-cm .cm-editor { flex: 1 1 auto; height: auto; min-height: 0; overflow: hidden; }
+.editor-body.editor-body-cm .fallback-editor { flex: 1 1 auto; height: auto; min-height: 0; resize: none; overflow: auto; }
 .editor-body-cm .cm-editor .cm-scroller { font-family: var(--font-mono); font-size: 13.5px; line-height: 1.75; }
 .editor-footer { height: 26px; min-height: 26px; display: flex; align-items: center; justify-content: space-between; padding: 0 12px; background: var(--bg-secondary); border-top: 1px solid var(--border); font-size: 11px; color: var(--text-muted); flex-shrink: 0; }
 .editor-stat-file { color: var(--text-secondary); max-width: 320px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
@@ -3555,17 +3563,16 @@ select {
 .help-tip-card {
   padding: 16px;
 }
+/* BUG-045: inside the editor, the CodeMirror scroller is the ONLY scroll
+   surface. `#editor-body` stays `overflow:hidden` (BUG-020 rule below) and
+   the scroller fills it — otherwise the body and the scroller scroll
+   together and render two stacked scrollbars. */
 .cm-editor {
-  height: auto;
-  min-height: 100%;
   font-size: 0.9rem;
 }
 .cm-scroller {
   font-family: "JetBrains Mono", monospace;
-  overflow-y: auto !important;
   overflow-x: auto !important;
-  height: auto;
-  min-height: 100%;
   max-width: 100%;
 }
 .fallback-editor {

frontend/sw.js

@@ -11,7 +11,7 @@
  * cache or Cloudflare does NOT clear the Service Worker Cache Storage, which is
  * a separate store. Bumping SW_VERSION invalidates it on every release.
  */
-const SW_VERSION = 'v19';
+const SW_VERSION = 'v20';
 const CODE_CACHE = `obsigate-code-${SW_VERSION}`;
 const RUNTIME_CACHE = `obsigate-runtime-${SW_VERSION}`;
 const API_CACHE = `obsigate-api-${SW_VERSION}`;