feat(filter): focus one game at a time

Switching games on and off says which games you play, and is set once.
It's the wrong tool for what a player of four games does while reading —
clear one game, move to the next — which cost two taps per game and left
the settings panel no longer describing what they play.

Focus is a lens over that filter, not a second filter: a bar at the top,
above everything it narrows, with a "next game" control that steps
through and ends by returning to all. It never touches hiddenGames, and
a focus on a game since switched off is ignored rather than obeyed, so
it can't strand you on a blank page whose cause is elsewhere. Each chip
carries that game's outstanding count, so a game with nothing waiting
says so before you visit it.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

src/client/components/Dailies.tsx

@@ -73,9 +73,9 @@ export function Dailies({
     previous.current = { total, complete };
     if (was === null || !allDone) return;
     // Celebrate finishing the last one, and only that. The list also gets
-    // shorter when the reader marks a repeating event done, which can land on
-    // "all complete" without them having ticked anything — a burst there is the
-    // app congratulating them for filtering.
+    // shorter when the reader focuses a single game or marks a repeating event
+    // done, which can land on "all complete" without them having ticked
+    // anything — a burst there is the app congratulating them for filtering.
     if (was.total === total && complete > was.complete) setBurst((n) => n + 1);
   }, [total, complete, allDone]);