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.

tests/frontend/ai.test.mjs

@@ -404,6 +404,73 @@ async function main() {
       panel.remove();
     });
 
+    await test("add action delegates to the Forge iframe when no CodeMirror is open (BUG-057)", () => {
+      const b = new BooksLM();
+      const panel = b._render();
+      b._panel = panel;
+      document.body.appendChild(panel);
+      b._messages = [{ role: "assistant", content: "Réponse Forge" }];
+      b._renderMessages();
+      state.editorView = null;
+      const iframe = document.createElement("iframe");
+      iframe.id = "forge-iframe";
+      document.body.appendChild(iframe);
+      const posted = [];
+      iframe.contentWindow.postMessage = (msg) => posted.push(msg);
+      panel.querySelector(".bookslm-msg.assistant .bookslm-msg-action-insert").click();
+      assert.equal(posted.length, 1, "one postMessage to the Forge iframe");
+      assert.equal(posted[0].type, "parent-insert");
+      assert.ok(posted[0].text.includes("Réponse Forge"), "answer forwarded");
+      iframe.remove();
+      panel.remove();
+    });
+
+    await test("add action falls back to the plain textarea editor", () => {
+      const b = new BooksLM();
+      const panel = b._render();
+      b._panel = panel;
+      document.body.appendChild(panel);
+      b._messages = [{ role: "assistant", content: "Réponse textarea" }];
+      b._renderMessages();
+      state.editorView = null;
+      const ta = document.createElement("textarea");
+      ta.value = "Ligne existante";
+      document.body.appendChild(ta);
+      ta.setSelectionRange(ta.value.length, ta.value.length);
+      state.fallbackEditorEl = ta;
+      panel.querySelector(".bookslm-msg.assistant .bookslm-msg-action-insert").click();
+      assert.ok(ta.value.includes("Réponse textarea"), "answer appended to the textarea");
+      state.fallbackEditorEl = null;
+      ta.remove();
+      panel.remove();
+    });
+
+    await test("code block exposes an add-section button inserting only the block (#102)", () => {
+      const b = new BooksLM();
+      const panel = b._render();
+      b._panel = panel;
+      document.body.appendChild(panel);
+      b._messages = [{
+        role: "assistant",
+        content: "Voici la section :\n\n```markdown\n## Titre\n\nContenu\n```\n\nFin.",
+      }];
+      b._renderMessages();
+      const btn = panel.querySelector(".bookslm-msg.assistant .bookslm-code-insert");
+      assert.ok(btn, "per-block add button rendered");
+      const dispatched = [];
+      state.editorView = {
+        state: { selection: { main: { to: 0 } } },
+        dispatch: (spec) => dispatched.push(spec),
+        focus: () => {},
+      };
+      btn.click();
+      assert.equal(dispatched.length, 1, "editor dispatch called");
+      assert.ok(dispatched[0].changes.insert.includes("## Titre"), "block content inserted");
+      assert.ok(!dispatched[0].changes.insert.includes("```"), "code fences stripped");
+      state.editorView = null;
+      panel.remove();
+    });
+
     await test("manual wheel scroll releases the top-pinning", async () => {
     const b = new BooksLM();
     const panel = b._render();

tests/frontend/editor-inline.test.mjs

@@ -347,6 +347,13 @@ test("editor-poc.html reloads Forge buffer on parent-reload", () => {
   assert.match(handler[1], /loadFile\(\);/);
 });
 
+test("editor-poc.html inserts assistant text on parent-insert (BUG-057)", () => {
+  assert.match(forgeSrc, /if \(e\.data\.type === 'parent-insert' && typeof e\.data\.text === 'string'\) \{/);
+  const handler = forgeSrc.match(/if \(e\.data\.type === 'parent-insert' && typeof e\.data\.text === 'string'\) \{([\s\S]*?)\n    \}/);
+  assert.ok(handler, "parent-insert handler not found");
+  assert.match(handler[1], /insertAtCursor\(/);
+});
+
 test("style.css lets the inline editor fill the content area", () => {
   assert.match(cssSrc, /\.editor-modal\.editor-inline-mode \{/);
   assert.match(cssSrc, /\.editor-modal\.editor-inline-mode \{[\s\S]*?pointer-events: none;/);