Save the match every second instead of waiting to be told

A force-quit deep into a turn came back at the clock's last-turn-switch value,
losing the whole interrupted turn. The tell was the delay counter returning at
a full 12: the newest saved state was the one tap() writes, and tap() sets
turnAt and calls saveGame() in the same breath, so it carries held ~ 0.
Restoring it reproduces the moment of the turn switch exactly.

The two triggers meant to save at quit time — visibilitychange and pagehide —
do not fire in Android's WebView. MainActivity's onPause() forwards to
web.onPause() under a comment claiming that is what makes visibilitychange
fire. It isn't: document visibility follows the WebView's view and window
visibility, not that call. The forwarding is still right for stopping timers
and audio, but the saved match should never have depended on it.

This is not new. It has almost certainly been broken since 1.0, and the release
check could not catch it, because for the first 12 seconds of a turn the delay
absorbs everything and render() never touches st.reserve. A clock that has lost
its place is indistinguishable from one that is correctly sitting still, so
every force-quit test that quit soon after a turn change passed. RELEASING.md
now says to let the turn run 40 seconds first, which is the only version of
that check worth running.

So the page stops waiting to be told. A timer writes the match once a second
while a clock is running — a timer rather than a hook in loop(), because
requestAnimationFrame stops when the page is hidden, which is exactly when this
matters. blur joins the listeners too: a different signal, and one that does
fire when the task switcher opens. At most a second can now be lost, which is
well inside the delay nobody is charged for anyway.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

RELEASING.md

@@ -61,6 +61,14 @@ make some moves, force-quit from the task switcher and reopen — everything
 should come back, paused. That is the check that proves the app's storage is
 working, and it fails silently rather than loudly.
 
+**Let the turn run at least 40 seconds before you quit.** This is the whole
+check, and doing it any faster proves nothing: for the first 12 seconds of a
+turn the delay absorbs everything and the reserve clock is *supposed* to sit
+still, so a clock that has lost its place looks exactly like one that hasn't.
+Quit well past the delay and the time must come back lower than it was at the
+turn switch — and the delay counter must not be sitting at a full 12. That is
+how a broken save hid from this check from 1.0 to 1.3.
+
 ## 5. Commit, tag, push
 
 ```bash