Fix sidebar toggle, ? shortcut, footer hint styling

- Sidebar: replace 32px overflow:hidden collapse with display:none — eliminates pointer-event/layout issues; button label toggles between 'Filters' and 'Show Filters'
- Keyboard shortcut ?: fix keydown handler to omit shift+ prefix for symbol keys (shift state already encoded in e.key), so '?' registration matches correctly
- Footer: add missing CSS for .lt-footer-hint, .lt-footer-key, .lt-footer-sep — resets button defaults so CFG/HELP render identically to link-style hints

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/css/base.css

@@ -1449,11 +1449,7 @@ select option:checked {
   border: 1px solid var(--border-color);
   transition: var(--transition-default);
 }
-.lt-sidebar.collapsed { width: 32px; overflow: hidden; }
-.lt-sidebar.collapsed .lt-sidebar-body { display: none; }
-.lt-sidebar.collapsed .lt-sidebar-header { justify-content: center; padding: 0.5rem 0; border-bottom: none; }
-.lt-sidebar.collapsed .lt-sidebar-header > span:first-child { display: none; }
-.lt-sidebar.collapsed .lt-sidebar-toggle { font-size: 0.8rem; padding: 0.4rem; color: var(--accent-cyan); }
+.lt-sidebar.collapsed { display: none; }
 
 .lt-sidebar-header {
   display: flex;
@@ -5589,6 +5585,33 @@ body.lt-is-offline .lt-main { margin-top: 2rem; transition: margin-top 0.25s eas
   .lt-footer { flex-direction: column; align-items: flex-start; gap: 0.25rem; }
 }
 
+.lt-footer-hints { display: flex; align-items: center; flex-wrap: wrap; gap: 0.25rem; }
+
+.lt-footer-hint {
+  /* reset button defaults */
+  all: unset;
+  cursor: pointer;
+  display: inline-flex;
+  align-items: center;
+  gap: 0.25rem;
+  color: var(--text-muted);
+  font-size: 0.7rem;
+  font-family: var(--font-mono);
+  white-space: nowrap;
+}
+.lt-footer-hint:hover { color: var(--accent-cyan); }
+.lt-footer-hint:focus-visible { outline: 1px dashed var(--accent-cyan); outline-offset: 2px; }
+
+.lt-footer-key {
+  color: var(--accent-cyan);
+  opacity: 0.8;
+}
+
+.lt-footer-sep {
+  color: var(--border-dim);
+  user-select: none;
+}
+
 /* ================================================================
    BLINKING CURSOR
    <h1 class="lt-cursor">SYSTEM STATUS</h1>