feat: Editor POC — multi-zone toolbar mockup (TOOLBAR_DESIGN_ANALYSIS.md)

Add standalone /editor-poc page demonstrating all 5 toolbar zones:
- Zone 1: Top Fixed Bar (hamburger, title, AI glow button, save indicator)
- Zone 2a: Slash Command Menu (/ on empty line, 15 commands, filtering)
- Zone 2b: Bubble Menu (on text selection, formatting + AI dropdown)
- Zone 3: Floating Quick Insert (per-line, Image/PDF/Code/Table/AI)
- Zone 4: AI Side Panel (Ctrl+J toggle, chat, suggestions)
- Zone 5: Drag & Drop overlay with dashed border

Files:
- new: frontend/editor-poc.html (46KB standalone vanilla JS)
- backend/main.py: +/editor-poc route before catch-all
- frontend/index.html: Editor POC button in header menu
- frontend/js/config.js: initEditorPocBtn() function + export
- frontend/js/legacy.js: re-export initEditorPocBtn
- frontend/js/app.js + frontend/app.js: init call in both versions

backend/main.py

@@ -4039,6 +4039,14 @@ if FRONTEND_DIR.exists():
             return HTMLResponse(content=popout_file.read_text(encoding="utf-8"))
         raise HTTPException(status_code=404, detail="Popout template not found")
 
+    @app.get("/editor-poc")
+    async def serve_editor_poc():
+        """Serve the standalone Editor POC page (multi-zone toolbar demo)."""
+        poc_file = FRONTEND_DIR / "editor-poc.html"
+        if poc_file.exists():
+            return HTMLResponse(content=poc_file.read_text(encoding="utf-8"))
+        raise HTTPException(status_code=404, detail="Editor POC not found")
+
     @app.get("/{full_path:path}")
     async def serve_spa(full_path: str):
         """Serve the SPA index.html for all non-API routes."""

frontend/app.js

@@ -4069,6 +4069,15 @@
     });
   }
 
+  function initEditorPocBtn() {
+    var btn = document.getElementById("editor-poc-btn");
+    if (!btn) return;
+    btn.addEventListener("click", function() {
+      closeHeaderMenu();
+      window.open("/editor-poc", "_blank");
+    });
+  }
+
   function initHelpNavigation() {
     const helpContent = document.querySelector(".help-content");
     const helpBody = document.getElementById("help-body");
@@ -7819,6 +7828,7 @@
     initSidebarTabs();
     initHelpModal();
     initConfigModal();
+    initEditorPocBtn();
     initSidebarFilter();
     initSidebarResize();
     initEditor();

frontend/index.html

@@ -649,6 +649,30 @@
                                         >
                                     </span>
                                 </button>
+                                <button
+                                    class="menu-list-row menu-list-button"
+                                    id="editor-poc-btn"
+                                    type="button"
+                                    role="menuitem"
+                                >
+                                    <span
+                                        class="menu-list-icon"
+                                        aria-hidden="true"
+                                    >
+                                        <i
+                                            data-lucide="pencil"
+                                            style="width: 17px; height: 17px"
+                                        ></i>
+                                    </span>
+                                    <span class="menu-list-content">
+                                        <span class="menu-list-title"
+                                            >Editor POC</span
+                                        >
+                                        <span class="menu-list-subtitle"
+                                            >Nouvel editeur (demo)</span
+                                        >
+                                    </span>
+                                </button>
                             </div>
                         </div>
                     </div>

frontend/js/app.js

@@ -38,6 +38,7 @@ async function init() {
   Legacy.initSidebarTabs();
   Legacy.initHelpModal();
   Legacy.initConfigModal();
+  Legacy.initEditorPocBtn();
   Sidebar.initSidebarFilter();
   UI.initSidebarResize();
   Utils.initEditor();

frontend/js/config.js

@@ -218,6 +218,14 @@ function initHelpModal() {
   });
 }
 
+function initEditorPocBtn() {
+  var btn = document.getElementById("editor-poc-btn");
+  if (!btn) return;
+  btn.addEventListener("click", function() {
+    window.open("/editor-poc", "_blank");
+  });
+}
+
 function initHelpNavigation() {
   const helpBody = document.getElementById("help-body");
   const navList = document.getElementById("help-nav-list");
@@ -1289,6 +1297,7 @@ export {
   initHelpModal,
   closeHelpModal,
   initRecentTab,
+  initEditorPocBtn,
   loadAbout as initAboutSection,
   loadHiddenFilesSettings as initHiddenFilesConfig,
   switchSidebarTab,

frontend/js/legacy.js

@@ -25,7 +25,7 @@ import {
 } from './dashboard.js';
 
 // --- Re-exports from modules that already have these functions ---
-export { initSidebarTabs, initConfigModal, initHelpModal, initRecentTab } from './config.js';
+export { initSidebarTabs, initConfigModal, initHelpModal, initRecentTab, initEditorPocBtn } from './config.js';
 export { initSyncStatus } from './sync.js';
 export { DashboardRecentWidget } from './dashboard.js';