Slate v2 before/after path support should reuse the current node range

What happened

Once Editor.before(...) and Editor.after(...) had honest Point | Range support, the next hole was Path.

The tempting lie was to bolt on a second path-walking branch that guessed at the relevant edge directly.

That would have duplicated logic the core already exposes through getCurrentRangeForPath(...).

What fixed it

The honest cut is tiny:

1. resolve Path to the current node range
2. reuse the existing Range edge logic
3. step through the same location seam as Point / Range

That keeps Path support as a thin adapter instead of a separate walking implementation.

Reusable rule

For Slate v2 location helpers:

• if Path means “the current node range”, resolve it once and reuse the existing Range path
• do not add a second path-specific stepping algorithm

If Path support and Range support walk differently, one of them is wrong.