Slate v2 Op-family Twenty-second Slice

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

Goal

• Broaden explicit non-empty Range deletion across adjacent mixed-inline sibling leaves inside one supported top-level block.

Scope

• Keep the slice to adjacent sibling-leaf crossings only.
• Support:
  • explicit non-empty Range
  • current non-empty selection when at is omitted
• Keep deletion inside one supported top-level block.
• Avoid arbitrary multi-leaf or cross-block range deletion in this slice.

Phases

• Confirm the adjacent mixed-inline range-delete semantics and current helper seams
• Write focused failing tests
• Implement the smallest honest core/API slice
• Sync package/public docs
• Verify the touched package/docs