Slate v2 Op-family Twenty-seventh Slice

Supporting plan. For current queue and roadmap truth, see master-roadmap.md.

Goal

• Land honest Path support for Editor.before(...) / Editor.after(...).

Scope

• Support Path by reusing the current node range.
• Keep the current Point | Range semantics unchanged.
• Support:
  • top-level block paths
  • supported mixed-inline descendant paths
• Avoid voids and unsupported-path parity in this slice.

Phases

• Confirm the Path before/after semantics and current location seams
• Write focused failing tests
• Implement the smallest honest Path support via getCurrentRangeForPath(...)
• Sync package/public docs
• Verify the touched package/docs