fix(ui): scroll selected item into view on slash command dropdown keyboard navigation (closes #838)

* fix(ui): scroll selected item into view on slash command dropdown keyboard nav

navigateCmdDropdown() in commands.js now calls scrollIntoView({block:'nearest'})
after updating the .selected class, so the highlighted item stays visible
when the dropdown overflows and the user navigates with ↓/↑. Closes #838.

* test: lock in scrollIntoView for slash command dropdown navigation (#838)

4 regression tests in test_cmd_dropdown_scroll_838.py:
- navigateCmdDropdown calls scrollIntoView on the selected item
- Uses {block:"nearest"} (minimum-distance scroll, not jumpy)
- Scroll call comes AFTER the .selected classList.add (correct target)
- .cmd-dropdown has overflow-y:auto so the dropdown itself is the scroll
  container (scrollIntoView does not bubble up to the viewport)

Full suite: 1749 passed, 0 failures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: nesquena-hermes <nesquena-hermes@users.noreply.github.com>
Co-authored-by: Nathan Esquenazi <nesquena@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

static/commands.js

@@ -733,6 +733,9 @@ function navigateCmdDropdown(dir){
   if(_cmdSelectedIdx<0)_cmdSelectedIdx=items.length-1;
   if(_cmdSelectedIdx>=items.length)_cmdSelectedIdx=0;
   items[_cmdSelectedIdx].classList.add('selected');
+  // Scroll the newly highlighted item into view so it stays visible when the
+  // dropdown overflows and the user navigates with keyboard (#838).
+  items[_cmdSelectedIdx].scrollIntoView({block:'nearest'});
 }
 
 function selectCmdDropdownItem(){