V2 Phase 5+6: connectivity, presence, navigation & friction

Phase 5 — live-session & multi-device hardening:
- connectivityStore + SyncStatusIndicator in the shell: shows "Offline" when the
  browser is offline and the cloud autosave state (saving / saved / failed) when
  signed in; useCloudAutosave now reports its status. Owns online/offline events.
- server presence heartbeat: protocol-level ping/pong per socket terminates a
  vanished connection (~30s), so a player who closes their laptop drops out of
  the GM's roster instead of lingering. No client changes needed.

Phase 6 — onboarding & friction:
- navigation: surfaced the previously orphaned routes in the rail — a new
  "World" group (Notes, NPCs, Quests, Calendar) and Homebrew + Assistant under
  Reference. (Empty-state hints and map rename already existed.)
- combat keyboard control: n/→ next turn, p/← previous turn, guarded so it never
  fires while typing; button tooltips document it.

Test hygiene: scoped now-ambiguous nav links in e2e to the Primary landmark, and
fixed pre-existing stale emoji selectors in the realtime suite (📡 Host → Host,
📨 Just for you → Just for you) left over from the Living Codex emoji purge.

Gate green: tsc + 277 unit + 34 e2e + 2 realtime. App + server build clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

e2e-realtime/seats.spec.ts

@@ -19,7 +19,7 @@ test('a player claims a seat and manages their character; edits round-trip to th
   await gm.getByLabel('Settings').click();
   await gm.getByRole('button', { name: 'Load sample campaign' }).click();
   await expect(gm.getByRole('heading', { name: 'Sample: Lost Mine' })).toBeVisible();
-  await gm.getByRole('button', { name: '📡 Host' }).click();
+  await gm.getByRole('button', { name: 'Host' }).click();
   const code = (await gm.getByTestId('join-code').textContent())?.replace(/[^A-Z0-9]/g, '') ?? '';
   expect(code).toHaveLength(6);