fix(search): don't open the command palette via Cmd/Ctrl+K while typing (#1414)

The global command palette's Cmd/Ctrl+K shortcut fired even when a text
field or the code editor held focus, stealing focus mid-edit and, on
macOS, clobbering the native Ctrl+K delete-to-end-of-line. Guard the
handler with isInputFocused() so the shortcut opens search only when the
user is not typing in a field; the toolbar search icon still opens it
from anywhere. Add unit tests for the keyboard path.

frontend/src/components/GlobalCommandPalette.tsx

@@ -18,6 +18,7 @@ import {
 } from '@/components/ui/command';
 import { DialogDescription, DialogTitle } from '@/components/ui/dialog';
 import { useNodes, type Node } from '@/context/NodeContext';
+import { isInputFocused } from '@/lib/keyboard-guards';
 import { cn } from '@/lib/utils';
 import {
     useCrossNodeStackSearch,
@@ -51,6 +52,10 @@ export function GlobalCommandPaletteProvider({ children }: { children: ReactNode
                 // Let cmdk's own Ctrl+K handling take precedence when focus is already inside a palette
                 const target = e.target as HTMLElement | null;
                 if (target?.closest('[cmdk-root]')) return;
+                // Don't hijack Cmd/Ctrl+K while the user is typing in a field or the code
+                // editor: stealing focus mid-edit is surprising, and on macOS Ctrl+K is the
+                // native delete-to-end-of-line. Search still opens elsewhere, or via the icon.
+                if (isInputFocused()) return;
                 e.preventDefault();
                 setOpen(prev => !prev);
             }