An admin area a phone could reach and not navigate

Administration has a nav of its own rather than the chat sidebar, and 1.1.0
gave every `.sidebar` the drawer behaviour -- starts closed, slides in --
without giving that one any of the drawer's furniture. No id for the toggle to
resolve, no toggle, no close, no scrim: it sat at left:-280 with nothing in the
application able to open it. The close button and the scrim are partials now,
used by both, and the test that guards it *finds* sidebars by scanning the
templates rather than working from a list, which is exactly why this one was
missed.

The chat, measured at 390px, spent forty pixels of side padding and a
forty-four pixel avatar column before drawing a word -- close to a quarter of
the screen on margin, so anything that could not wrap had to be reached
sideways. Padding halved and the avatar moved above the turn; a code block
gained about sixty pixels.

Worse in the same row: `.topbar__actions` asked for 317px of a 390px bar,
because the control that used to give in that row is display:none below a
tablet width, so the group went rigid and the title -- flex: 1 -- was squeezed
to exactly zero. And `.btn--icon` sets a width with no `flex: none`, so the row
shrank the button instead of the text: the sidebar toggle measured eighteen
pixels across. The picker gives now, and shows its avatar rather than its name
on a phone.

Also the instrument, which lied twice more: it could not see horizontal
overflow at all, because `.shell` is overflow:hidden and its "is this
contained" test therefore answered yes for everything on the page; and run from
a copy it resolved `STATIC` to a directory that did not exist, rewrote every
asset URL to a dead file:// path and reported the whole application overflowing
by thirty thousand pixels. It resolves from the imported package now and
asserts that what it rewrote to is really there.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/lembas/web/templates/admin/_layout.html

@@ -14,10 +14,20 @@
 
 {% block body %}
 <div class="shell">
-  <aside class="sidebar">
-    <div class="sidebar__header">
-      {{ brandlink(uid="admin") }}
-    </div>
+  {#
+    `id="sidebar"` and the drawer's furniture, because below the phone
+    breakpoint `.sidebar` is a fixed overlay that starts closed -- and this one
+    had neither an id for `data-toggle="#sidebar"` to find nor any control to
+    open it. The administration area was reachable on a phone and then
+    unnavigable once you arrived.
+  #}
+  <aside class="sidebar" id="sidebar">
+    <header class="sidebar__header">
+      <div class="sidebar__brand-slot">
+        {{ brandlink(uid="admin") }}
+      </div>
+      {% include "partials/_sidebar_close.html" %}
+    </header>
 
     <nav class="sidebar__scroll" aria-label="Administration">
       <div class="nav-group">
@@ -106,8 +116,11 @@
     </div>
   </aside>
 
+  {% include "partials/_sidebar_scrim.html" %}
+
   <main class="main">
     <header class="topbar">
+      {% include "partials/_sidebar_toggle.html" %}
       <h1 class="topbar__title">{% block heading %}Administration{% endblock %}</h1>
       <button class="btn btn--icon" type="button" data-theme-toggle aria-label="Switch theme">
         <span class="theme-icon theme-icon--dark">{{ icon("moon") }}</span>