Add global keyboard EventRouter and unify publish (M6, §01D)

One module owns the document keydown listener and dispatches the shortcut map
(Cmd/Ctrl+Shift+N / +K / +S / +, / Escape), platform-aware, via the single-source
focus-utils interactive-context gate. Escape and Cmd/Ctrl+S run before the gate so
save works while editing; the rest are suppressed mid-typing. Publish + its toast
move into services/snippet-actions so the button and Cmd/Ctrl+S behave identically.
Removes the ad-hoc keydown handler from App and Monaco's Cmd+S command.

src/app/App.tsx

@@ -8,8 +8,7 @@ import { SnippetLibrary } from './components/SnippetLibrary';
 import { SpecEditor } from './components/SpecEditor';
 import { ThemeToggle } from './components/ThemeToggle';
 import { Toaster } from './components/Toaster';
-import { openModal, setConfirm, toggleDatasets } from './modals/ModalCoordinator';
-import { openSettingsPopover } from './stores/SettingsPopoverStore';
+import { openModal, setConfirm } from './modals/ModalCoordinator';
 import { confirm } from './stores/ConfirmStore';
 import { usePanesStore } from './stores/PanesStore';
 import { exportWorkspace, importWorkspace } from './services/transfer';
@@ -47,24 +46,6 @@ export function App() {
     setConfirm((message) => confirm({ title: 'Discard changes?', message, danger: true }));
   }, []);
 
-  // Cmd/Ctrl+K toggles the Datasets manager (spec §05); Cmd/Ctrl+, opens the
-  // editor settings popover — the primary preference cluster, now that settings
-  // are distributed per pane (spec §07). Full key router lands in M6 (arch 04).
-  useEffect(() => {
-    const onKey = (e: KeyboardEvent) => {
-      if (!(e.metaKey || e.ctrlKey)) return;
-      if (e.key === 'k' || e.key === 'K') {
-        e.preventDefault();
-        toggleDatasets();
-      } else if (e.key === ',') {
-        e.preventDefault();
-        openSettingsPopover('editor-settings');
-      }
-    };
-    window.addEventListener('keydown', onKey);
-    return () => window.removeEventListener('keydown', onKey);
-  }, []);
-
   const handleImportFile = (e: React.ChangeEvent<HTMLInputElement>) => {
     const file = e.target.files?.[0];
     // Reset the input so picking the same file again still fires onChange.