feat(footer): let the reader check for new data

A reload can be served the browser's cached feed for minutes. The button
beside the data's age asks the server past that copy, swaps in a newer
feed without reloading, and says honestly what came back. Newer is
judged on events and sources, never the build stamp. The age now says
"just now" rather than "ended ago" when a fresh feed is a moment ahead
of the page's clock.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/PRD.md

@@ -461,6 +461,13 @@ The footer shows when the feed was last updated, per game. If a game's data is m
 stale, its lane carries a warning badge. Never present stale data as current — the whole value
 proposition is trust in the dates.
 
+**The reader can ask for the newest data.** A reload is not enough — the browser may keep the feed
+for minutes — so *Check for new data* beside the age asks the server past that copy and swaps a newer
+feed in without a reload. It says what happened: updated, nothing newer published yet (sources are
+read about twice a day, and the button cannot make that sooner), or the server could not be reached.
+"Newer" is judged on events and source health, never on the build stamp. Disabled offline; nothing
+polls on its own.
+
 **The staleness notice names only the games the reader has switched on, and says that it does.**
 The headline age is about the feed and stays whole; the notice under it is an *instruction*, and the
 only remedy it offers is "go and check that game's source page" — which a reader cannot act on for a