[Mods] Let a Button with children style its keyboard-focus ring

Claude Code 2.1.296.

Since 2.1.295 a Button can hold Text children, so a list row can be one pressable control
instead of a row of text with one small Button in it. Under the pointer the row can keep its own
look: hover takes Text style overrides, and hover: { inverse: false } cancels the inversion.

Under keyboard focus nothing can be overridden. The ring inverts the whole Button, so a list row
that carries a selection background and a coloured chip turns into a white bar with the chip
drawn black. A row that held autoFocus, such as the current task in a list, shows that bar
whenever the pane takes the keyboard.

Request: a focus prop on ButtonProps taking the same Text style overrides as hover, or
hover applying under the focus ring as well as the pointer, as dimColor already does ("drawn
at full strength under the pointer or the focus").

Context: a mod drawing a task list wants the whole row to answer a click (the row already lights
up under the pointer through its Box hover), while the focused row keeps the list's own
selection style instead of a full-row inversion.