Slate v2 Op-family Twenty-fifth Slice

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

Goal

• Broaden collapsed delete(...) across adjacent supported top-level block boundaries.

Scope

• Keep the slice collapsed-delete only.
• Support:
  • explicit Point
  • current collapsed selection
  • reverse
  • distance
• Support adjacent supported top-level block crossings only.
• Require same-type/same-props block merges in this slice.
• Avoid multi-block deletion and cross-block explicit Range deletion in this slice.

Phases

• Confirm the adjacent cross-block delete semantics and current merge seam
• Write focused failing tests
• Implement the smallest honest adjacent cross-block delete follow-on
• Sync package/public docs
• Verify the touched package/docs