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/services/snippet-actions.test.ts

@@ -0,0 +1,35 @@
+import { beforeEach, describe, expect, test } from 'vitest';
+import { createSnippet } from '@core/snippet';
+import { useNotificationStore } from '../stores/NotificationStore';
+import { useSnippetStore } from '../stores/SnippetStore';
+import { publishActiveSnippet } from './snippet-actions';
+
+const T = new Date('2026-06-01T00:00:00Z');
+const snippets = () => useSnippetStore.getState();
+const toasts = () => useNotificationStore.getState().notifications;
+
+beforeEach(() => {
+  useSnippetStore.getState().reset();
+  useNotificationStore.getState().clear();
+});
+
+describe('publishActiveSnippet', () => {
+  test('publishes the active draft and raises one success toast', () => {
+    snippets().hydrate([createSnippet({ id: 'a', now: T })], 'a');
+    snippets().updateDraft('{"published":1}');
+
+    publishActiveSnippet();
+
+    expect(snippets().snippets.find((s) => s.id === 'a')?.spec).toBe('{"published":1}');
+    expect(toasts()).toHaveLength(1);
+    expect(toasts()[0]).toMatchObject({ kind: 'success', title: 'Snippet published' });
+  });
+
+  test('is a silent no-op when no snippet is active', () => {
+    snippets().hydrate([], null);
+
+    publishActiveSnippet();
+
+    expect(toasts()).toHaveLength(0);
+  });
+});

src/app/services/snippet-actions.ts

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+/**
+ * Snippet action helpers that pair a store mutation with its user-facing
+ * confirmation, so every trigger of an action behaves identically.
+ *
+ * `publishActiveSnippet` is the single publish-with-confirmation path: the
+ * Publish button (SpecEditor) and the Cmd/Ctrl+S shortcut (EventRouter) both go
+ * through it, so the success toast (spec §03D) fires no matter how the user
+ * published. Without this, Cmd+S published silently while the button toasted — a
+ * trigger-dependent inconsistency.
+ */
+
+import { notify } from '../stores/NotificationStore';
+import { useSnippetStore } from '../stores/SnippetStore';
+
+/**
+ * Publish the active snippet's draft and confirm it. No-op (no toast) when no
+ * snippet is active. The toast copy follows the council's rule (architecture 10
+ * → Toast copy): the title states the action, the message adds the consequence.
+ */
+export function publishActiveSnippet(): void {
+  if (!useSnippetStore.getState().activeSnippetId) return;
+  useSnippetStore.getState().publish();
+  notify({
+    kind: 'success',
+    title: 'Snippet published',
+    message: 'Your draft is now the published version.',
+  });
+}