feat(nav): refonte du layout — barre latérale repliable, topbar mince (issue #16)

Retour de Bruno sur la 0.15.0 (disposition pas conviviale, trop
de place, mobile inchangé): la barre horizontale disparaît.
Barre latérale groupée (Principal/Rituels/Pilotage/Outils),
repliable en rail d'icônes mémorisé sur desktop, tiroir
hors-canvas sur mobile; topbar de 52px (fil d'Ariane + actions).

static/js/nav.js

@@ -1,55 +1,45 @@
 /**
- * Kanbante — header navigation (issue #16): the "Plus" dropdown on
- * desktop and the burger panel on mobile. One shared partial
- * (_header.html), one shared behaviour: this file.
+ * Kanbante — sidebar behaviour (issue #16, 0.16.0 layout).
+ * Desktop: collapse to an icon rail (persisted in localStorage).
+ * Mobile: the same sidebar becomes an off-canvas drawer, toggled
+ * by the topbar burger, closed by backdrop / Escape / navigation.
  */
 (function () {
-    var moreBtn = document.getElementById('nav-more-btn');
-    var moreMenu = document.getElementById('nav-more-menu');
     var burger = document.getElementById('nav-burger');
-    var mobileNav = document.getElementById('mobile-nav');
+    var backdrop = document.getElementById('side-backdrop');
+    var collapseBtn = document.getElementById('side-collapse');
 
-    function setOpen(menu, btn, open) {
-        if (!menu || !btn) return;
-        menu.hidden = !open;
-        btn.setAttribute('aria-expanded', open ? 'true' : 'false');
-    }
-    function closeAll() {
-        setOpen(moreMenu, moreBtn, false);
-        setOpen(mobileNav, burger, false);
+    function closeDrawer() {
+        document.body.classList.remove('sidebar-open');
+        if (backdrop) backdrop.hidden = true;
         if (burger) {
+            burger.setAttribute('aria-expanded', 'false');
             burger.textContent = '☰';
-            burger.setAttribute('aria-label', 'Ouvrir le menu');
         }
     }
 
-    if (moreBtn && moreMenu) {
-        moreBtn.addEventListener('click', function (e) {
-            e.stopPropagation();
-            var willOpen = moreMenu.hidden;
-            closeAll();
-            setOpen(moreMenu, moreBtn, willOpen);
-        });
-        moreMenu.addEventListener('click', function (e) { e.stopPropagation(); });
-    }
-    if (burger && mobileNav) {
-        burger.addEventListener('click', function (e) {
-            e.stopPropagation();
-            var willOpen = mobileNav.hidden;
-            closeAll();
-            setOpen(mobileNav, burger, willOpen);
-            burger.textContent = willOpen ? '✕' : '☰';
-            burger.setAttribute('aria-label', willOpen ? 'Fermer le menu' : 'Ouvrir le menu');
+    if (burger) {
+        burger.addEventListener('click', function () {
+            var open = document.body.classList.toggle('sidebar-open');
+            burger.setAttribute('aria-expanded', open ? 'true' : 'false');
+            burger.textContent = open ? '✕' : '☰';
+            if (backdrop) backdrop.hidden = !open;
         });
     }
-    document.addEventListener('click', function () { closeAll(); });
+    if (backdrop) backdrop.addEventListener('click', closeDrawer);
     document.addEventListener('keydown', function (e) {
-        if (e.key === 'Escape') closeAll();
+        if (e.key === 'Escape') closeDrawer();
     });
     window.addEventListener('resize', function () {
-        if (window.innerWidth > 900) {
-            closeAll();
-            if (burger) burger.textContent = '☰';
-        }
+        if (window.innerWidth > 900) closeDrawer();
     });
+
+    if (collapseBtn) {
+        collapseBtn.addEventListener('click', function () {
+            var collapsed = document.body.classList.toggle('sidebar-collapsed');
+            try {
+                localStorage.setItem('kanbante-sidebar', collapsed ? 'collapsed' : 'open');
+            } catch (e) { /* private mode: state lasts for the page only */ }
+        });
+    }
 })();