refactor: replace inline onclick with data-action event delegation

The command palette button used an inline onclick handler while every
other interactive element in base.html uses data-action + event
delegation. Now consistent: data-action="open-cmdpalette" handled in
the global footer click listener.

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

templates/base.html

@@ -144,9 +144,9 @@
       <!-- ⌘K affordance -->
       <button type="button"
               class="lt-btn lt-btn-ghost lt-btn-sm lt-cmd-hint-btn"
+              data-action="open-cmdpalette"
               title="Command palette (Ctrl+K)"
-              aria-label="Open command palette"
-              onclick="if(window.lt&&lt.cmdPalette)lt.cmdPalette.open()">&#x2315;&nbsp;K</button>
+              aria-label="Open command palette">&#x2315;&nbsp;K</button>
 
       <button type="button" class="lt-theme-btn" id="lt-theme-btn"
               aria-label="Toggle theme" title="Toggle light/dark mode">&#x2600;</button>
@@ -346,8 +346,9 @@
       const btn = e.target.closest('[data-action]');
       if (!btn) return;
       const action = btn.getAttribute('data-action');
-      if (action === 'show-keyboard-help' && window.lt)  lt.modal.open('lt-keys-help');
-      if (action === 'open-settings' && window.lt)       lt.modal.open('lt-settings-modal');
+      if (action === 'open-cmdpalette' && window.lt && lt.cmdPalette) lt.cmdPalette.open();
+      if (action === 'show-keyboard-help' && window.lt)               lt.modal.open('lt-keys-help');
+      if (action === 'open-settings' && window.lt)                    lt.modal.open('lt-settings-modal');
     });
 
     lt.keys.on('r', function() { lt.autoRefresh.now(); });