fix: intercept Tab key to prevent browser focus navigation

Tab key was being captured by the browser for focus cycling instead of
being sent to the terminal for bash completion. Now intercepted at the
document level and forwarded to the terminal when xterm has focus.

static/toolbar.js

@@ -111,6 +111,18 @@
     if(btn.dataset.k) send(btn.dataset.k);
   });
 
+  // Prevent browser from stealing Tab key — send it to the terminal instead
+  document.addEventListener('keydown', function(e){
+    if(e.key === 'Tab' && !e.altKey && !e.ctrlKey && !e.metaKey){
+      var active = document.activeElement;
+      // Only intercept if focus is on the terminal or body (not on toolbar buttons)
+      if(!active || active === document.body || active.closest('.xterm')){
+        e.preventDefault();
+        send('\t');
+      }
+    }
+  });
+
   // Shrink terminal for toolbar on mobile (2 rows)
   var obs=new MutationObserver(function(){
     var el=document.querySelector('.xterm');