Configurable width for a lone tiled window on any monitor

[JasonBates]

Problem

A single tiled window expands across nearly the full monitor. On an ordinary large display, a lone browser or writing window can be uncomfortably wide even when the monitor is not ultrawide. I also prefer a narrower lone window on my laptop. When a second window opens, normal tiling is useful again. (I've implemented a solution in a fork that I use day to day below)

Short animation

This schematic animation shows a lone window narrowing to 50% on a wide display, then normal tiling returning when a second window joins.

Desired behavior

An optional setting centres the sole tiled window at a configurable percentage of the current monitor's usable width. The percentage can vary by monitor width. Multiple tiled windows, floating windows and AeroSpace full screen retain their usual behavior. Without the setting, the existing layout stays unchanged.

Working solution / proof of concept

I have a fork and branch that demonstrates this implementation; commit 92be41f. It has its single-window-width-rules select 66% below 2000 scaled display points (my 1512-point laptop display) and 50% from 2000 points upward (my 2560-point Studio displays). The rules are editable for other display setups.

The branch adapts the single-window layout work in PR #2093 and adds monitor-width-dependent percentage rules. It is a working solution for my setup and a proof of concept for upstream.

I am using this working solution in my current AeroSpace build. I have also extended that build with Focus Mode (discussion #2309), which temporarily centres a chosen window and dims the others while preserving the tiled layout. The single-window width rules described here remain in use.

Related discussions

Issue #60 covers broader ultrawide support. Discussion #621 considers a per-monitor maximum width for tiled windows, including layouts with multiple windows. This proposal is narrower: it changes only the sole tiled window and applies to ordinary displays as well as ultrawides.

Would this focused single-window behavior be useful upstream, or should it be incorporated into the broader maximum-width design?