feat: add guarded GitHub Pages deployment

pages/release-clock.ts

@@ -0,0 +1,25 @@
+export type ReleaseClockSource = 'system';
+
+export type ReleaseClock = {
+  source: ReleaseClockSource;
+  now: () => number;
+};
+
+type ReleaseClockOptions = {
+  wallNow?: () => number;
+};
+
+function systemClock(wallNow: () => number): ReleaseClock {
+  return { source: 'system', now: wallNow };
+}
+
+export function createInitialReleaseClock(
+  _serverNow: unknown,
+  options: ReleaseClockOptions = {}
+): ReleaseClock {
+  return systemClock(options.wallNow ?? Date.now);
+}
+
+export async function synchronizeReleaseClock(options: ReleaseClockOptions = {}): Promise<ReleaseClock> {
+  return systemClock(options.wallNow ?? Date.now);
+}