File tree browser keyboard shortcuts conflict with browser native shortcuts (Cmd+L, Ctrl+K, etc.)

Summary

The repository file tree browser's onTreeKeydown handler in tree_list.vue intercepts single-letter key events without checking for modifier keys. This causes browser-native shortcuts like Cmd+L (focus address bar), Ctrl+K (search bar), Ctrl+L, etc. to be swallowed when the file tree has focus.

Reported in #581271 (comment 3133385101).

Root Cause

In app/assets/javascripts/repository/file_tree_browser/components/tree_list.vue, the onTreeKeydown method has an a-z type-ahead handler that matches any single letter keypress without excluding modifier key combos:

// a-z — currently does NOT check for modifier keys
if (/^[a-zA-Z]$/.test(event.key)) {
  event.preventDefault(); // This blocks Cmd+L, Ctrl+K, etc.
  ...
}

When a user presses Cmd+L, event.key is "l" which matches the regex, so event.preventDefault() is called and the browser shortcut is blocked.

Proposed Fix

Add modifier key guards to the a-z handler (and optionally the * handler):

// a-z (only when no modifier keys are pressed)
if (/^[a-zA-Z]$/.test(event.key) && !event.metaKey && !event.ctrlKey && !event.altKey) {
  event.preventDefault();
  ...
}

Alternatively, a top-level early return could be added at the beginning of onTreeKeydown to let all browser/OS shortcuts pass through:

onTreeKeydown(event) {
  // Allow all browser/OS shortcuts to pass through
  if (event.metaKey || event.ctrlKey) return;
  ...
}

The per-block guard is more precise if fine-grained control over modifier combos is desired.

Affected File

• app/assets/javascripts/repository/file_tree_browser/components/tree_list.vue — onTreeKeydown method

Steps to Reproduce

1. Navigate to any repository page with the file tree browser visible
2. Click on any file/directory in the file tree so it has focus
3. Press Cmd+L (macOS) or Ctrl+L (Windows/Linux)
4. Expected: Browser address bar is focused
5. Actual: The file tree jumps to a file starting with "L" and the browser shortcut is blocked