feat(dialog): restoreFocus — a fallback focus home for the close

[ivanbanov]

What

Dialog.Content gains restoreFocus, the close-side counterpart to initialFocus. Closing still restores focus to whatever held it before the dialog opened — but only when that element can meaningfully take focus back. When focus sat on the body (a pointer press can leave it there) or on an element removed from the document since, the restore falls back to the consumer-designated target, typically the trigger. With neither, focus stays where it is.

Where

• @dunky.dev/dom-dialog — the decision lives once in openDialogLayer: a new restoreFocus?: () => HTMLElement | null option, resolved at close, plus the meaningful-previous check (instanceof HTMLElement, not the body, still connected) in the disposer.
• @dunky.dev/react-dialog — restoreFocus?: RefObject<HTMLElement | null> on Dialog.Content, read through a ref at close time.
• @dunky.dev/solid-dialog — restoreFocus?: HTMLElement | (() => HTMLElement | null | undefined) on Dialog.Content, same shape as initialFocus, resolved at close time.

The bindings add no behavior — they only plumb their host idiom into the DOM option, per the one-way boundary.

Why

Both fallback cases previously dropped focus silently: restoring to the body goes nowhere, and focus() on a disconnected element is a no-op, leaving focus stranded on the closing layer. The element focused before opening still always wins when it is meaningful — the fallback never overrides it.

Coverage

• dom-dialog: priority of the meaningful previous over the designated target; body fallback; removed-holder fallback; no-target no-op.
• react/solid: the prop plumbed end to end (body-focused open, close restores to the designated element).
• SPECs updated: the open-edge restore contract in dom-dialog, prop tables in both substrates. Changeset: minor × 3.

Full suite green: 16 files, 281 tests. Typecheck (base + solid), oxlint, oxfmt clean.

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