feat: v0.16.1 — ISS-007 smooth client-side sim clock with per-snapshot re-sync

e2e/panes.spec.ts

@@ -4,6 +4,8 @@ import { test, expect, type Page } from '@playwright/test';
 // The panes render from the shell's single /api/state poll (lib/useGameState.ts); time
 // controls POST to /api/sim and refetch immediately, so UI assertions settle within a tick.
 
+const SCALE = 1000; // fastest sim speed — top of the v0.14.0 ladder (same convention as e2e/sim.spec.ts)
+
 interface SimState {
   clockMs: number;
   timeScale: number;
@@ -104,6 +106,40 @@ test('time controls: pause freezes the sim and the ladder slider sets timeScale'
   expect(after.simState.paused).toBe(false);
 });
 
+test('sim clock ticks smoothly between polls — seconds advance without waiting for a snapshot (ISS-007)', async ({ page }) => {
+  await page.goto('/');
+  const clock = page.getByTestId('sim-clock');
+  await expect(clock).toBeVisible({ timeout: 15_000 });
+
+  // Fastest scale so game seconds move visibly inside the sampling window.
+  const post = await page.request.post('/api/sim', { data: { timeScale: SCALE, paused: false } });
+  expect(post.status()).toBe(200);
+
+  // "YYYY-MM-DD HH:MM:SS UTC" → epoch ms (UTC). While running there is no "(paused)" suffix.
+  const sample = async () => {
+    const text = ((await clock.textContent()) ?? '').trim();
+    expect(text, `clock format: ${text}`).toMatch(/^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2} UTC$/);
+    return Date.parse(`${text.replace(' ', 'T')}Z`);
+  };
+
+  // Three samples ~1.3 s apart real time: at scale 1000 each gap is ≈1300 game seconds, so the
+  // displayed clock must strictly advance between CONSECUTIVE samples — with the old poll-only
+  // rendering a sample pair could straddle zero snapshot updates and show no change at all.
+  const t0 = await sample();
+  await new Promise((r) => setTimeout(r, 1_300));
+  const t1 = await sample();
+  await new Promise((r) => setTimeout(r, 1_300));
+  const t2 = await sample();
+
+  expect(t1).toBeGreaterThan(t0);
+  expect(t2).toBeGreaterThan(t1);
+  // Sanity: ~2.6 s real × 1000 ≈ 2.6 M game ms — generous bounds keep slow CI boxes safe while
+  // still catching a frozen or wildly mis-scaled clock.
+  const total = t2 - t0;
+  expect(total).toBeGreaterThanOrEqual(1_000_000);
+  expect(total).toBeLessThanOrEqual(6_000_000);
+});
+
 test('slider commit keeps the chosen scale on screen until confirmed — no snap-back (ISS-001)', async ({ page }) => {
   test.setTimeout(60_000);
   await page.goto('/');