feat(ai): ajouter une section de la reponse et supporter l'editeur Forge (BUG-057, #102)

L'assistant IA peut desormais inserer sa reponse dans l'editeur Forge (postMessage parent-insert) en plus d'Editer, et chaque bloc de code propose un bouton « Ajouter la section » pour n'inserer que ce bloc.

frontend/js/bookslm.js

@@ -2153,6 +2153,7 @@ class BooksLM {
       bubble.className = 'bookslm-bubble assistant';
       const { text, actions } = this._extractActions(msg.content || '');
       bubble.innerHTML = this._renderMarkdown(text);
+      this._enhanceCodeBlocks(bubble);
       // Plain chat has no steps block: the pending answer itself carries the
       // animated indicator until the first token arrives.
       if (running && !text && !actions.length) {
@@ -2234,28 +2235,90 @@ class BooksLM {
   }
 
   /**
-   * Append an assistant answer to the Forge editor document (Notion “Ajouter”).
-   * No-ops with a toast when no editor session is open.
+   * Append an assistant answer (or a single code block) to the document open
+   * in the active editor (Notion “Ajouter”). Supports the three editor
+   * surfaces: CodeMirror (« Editer »), the Forge iframe and the plain textarea
+   * fallback. No-ops with a toast when no editor session is open.
    */
   _insertIntoEditor(text) {
+    const value = String(text == null ? '' : text);
+    if (!value.trim()) return;
+
+    // 1. CodeMirror editor (« Editer »).
     const view = state.editorView;
-    if (!view || !view.state || typeof view.dispatch !== 'function') {
-      showToast(t('bookslm.insert_no_editor'), 'info');
+    if (view && view.state && typeof view.dispatch === 'function') {
+      try {
+        const at = view.state.selection.main.to;
+        const insert = (at > 0 ? '\n' : '') + value;
+        view.dispatch({
+          changes: { from: at, insert },
+          selection: { anchor: at + insert.length },
+        });
+        if (typeof view.focus === 'function') view.focus();
+        showToast(t('bookslm.inserted'), 'success');
+      } catch (e) {
+        console.warn('AI assistant: insert into editor failed', e);
+        showToast(t('bookslm.insert_no_editor'), 'error');
+      }
       return;
     }
-    try {
-      const at = view.state.selection.main.to;
-      const insert = (at > 0 ? '\n' : '') + text;
-      view.dispatch({
-        changes: { from: at, insert },
-        selection: { anchor: at + insert.length },
-      });
-      if (typeof view.focus === 'function') view.focus();
-      showToast(t('bookslm.inserted'), 'success');
-    } catch (e) {
-      console.warn('AI assistant: insert into editor failed', e);
-      showToast(t('bookslm.insert_no_editor'), 'error');
+
+    // 2. Forge editor (same-origin iframe): its buffer lives in the child
+    // document, so the insertion is delegated with a postMessage.
+    const forge = document.getElementById('forge-iframe');
+    if (forge && forge.contentWindow) {
+      try {
+        forge.contentWindow.postMessage({ type: 'parent-insert', text: value }, '*');
+        showToast(t('bookslm.inserted'), 'success');
+      } catch (e) {
+        console.warn('AI assistant: insert into Forge failed', e);
+        showToast(t('bookslm.insert_no_editor'), 'error');
+      }
+      return;
     }
+
+    // 3. Plain textarea fallback (CodeMirror failed to load).
+    const ta = state.fallbackEditorEl;
+    if (ta && typeof ta.value === 'string') {
+      const start = ta.selectionStart != null ? ta.selectionStart : ta.value.length;
+      const end = ta.selectionEnd != null ? ta.selectionEnd : ta.value.length;
+      const insert = (start > 0 ? '\n' : '') + value;
+      ta.value = ta.value.slice(0, start) + insert + ta.value.slice(end);
+      const pos = start + insert.length;
+      if (typeof ta.setSelectionRange === 'function') ta.setSelectionRange(pos, pos);
+      ta.dispatchEvent(new Event('input', { bubbles: true }));
+      if (typeof ta.focus === 'function') ta.focus();
+      showToast(t('bookslm.inserted'), 'success');
+      return;
+    }
+
+    showToast(t('bookslm.insert_no_editor'), 'info');
+  }
+
+  /**
+   * #102 — Add a discreet « Ajouter » button to every fenced code block of an
+   * answer, so a single proposed section can be inserted instead of the whole
+   * reply. The button reuses the message action styling.
+   */
+  _enhanceCodeBlocks(bubble) {
+    if (!bubble || typeof bubble.querySelectorAll !== 'function') return;
+    const blocks = bubble.querySelectorAll('pre');
+    blocks.forEach((pre) => {
+      const code = pre.querySelector('code');
+      if (!code) return;
+      const wrap = document.createElement('div');
+      wrap.className = 'bookslm-code-block';
+      pre.parentNode.insertBefore(wrap, pre);
+      wrap.appendChild(pre);
+      const btn = this._actionBtn(
+        t('bookslm.insert_block'),
+        'insert',
+        t('bookslm.insert_block_hint'),
+        () => this._insertIntoEditor(code.textContent),
+      );
+      btn.classList.add('bookslm-code-insert');
+      wrap.appendChild(btn);
+    });
   }
 
   _copyText(text) {