flushPage method
Flush a single page to the pager (if dirty). Used by CheckpointManager for incremental dirty-page flushing.
Implementation
Future<void> flushPage(int pageId) async {
// The existing PageCache.flushAll() writes all dirty pages.
// flushPage() is a targeted version — we call the internal
// write-through method for a single page.
//
// Implementation note: Since PageCache doesn't expose a per-page
// flush in its current API, we use the fact that put() marks pages
// dirty and get() reads them. The correct implementation adds a
// flushPage(int pageId) to PageCache.
//
// For now: call flushAll() which is idempotent and handles
// dirty-page tracking internally. In Phase 2, patch PageCache
// to expose a targeted flushPage().
await flushAll();
}