fix: let the settings panel use the width of the page

Looked at on a 1440px screen it was the one block on the page not using
the column it sits in. The rows were held to max-w-3xl inside an 1150px
shell, but the section's own rule spans the shell — so every hairline
inside the panel stopped a third of the column short of the one above it,
between a two-column checklist and a three-column footer that both go
full width. The measure was there to keep a name and its state reading as
one line, but that pairing is what "running now" already does with a
title and its countdown directly above, so full width is the house
pattern rather than a stretch. Prose inside a group keeps its measure.

The game list was the worse half: eighteen rows of four controls at
max-w-md is a thousand pixels of ribbon down the left with two thirds of
the screen empty beside it. It takes two columns past lg once there are
nine or more games, flowing down then across so the numbers still read in
a straight line and an arrow still swaps a row with its neighbour. Below
nine, and on a phone, it is unchanged.

The last group also loses its bottom rule, which was a second hairline a
few pixels above the footer's own.

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

docs/PRD.md

@@ -217,6 +217,15 @@ points at: the empty states name both the switch and the group it is in, which i
 a checkbox in a wall was. And **the summary states are derived, never stored** — they are a reading
 of `prefs`, so they cannot disagree with the controls inside.
 
+**The panel uses the page's width**, like every other block on it. The rows were held to a narrower
+measure on the argument that a name and its state stop reading as one line across a wide screen, but
+the panel's own rule spans the shell, so the rules inside it stopped a third of the column short and
+the panel became the one thing on a desktop page not using the width — sitting between a two-column
+checklist and a three-column footer that both do. A title at one end of a full-width row and its
+countdown at the other is what "running now" does directly above it. Prose inside a group keeps a
+readable measure, and the game list takes two columns of its own on a wide screen once there are nine
+or more games, because eighteen rows in one column is a thousand pixels of ribbon down the left.
+
 **F4a — Focus one game at a time.**
 Switching games on and off says *which games the reader plays*, and is set once. It is the wrong
 tool for the thing a player of four games actually does while reading: clear one game, move to the