Slate v2 remove_text should stay exact and rebase selection inward

What happened

After set_node / unsetNodes(...), the next missing low-level text seam was remove_text.

The tempting mistake was obvious:

• pretend legacy Transforms.delete(...) already exists
• or add a broad text-deletion helper with distance/unit semantics immediately

That would have lied about the current engine.

What fixed it

The honest slice stayed narrow:

1. add real remove_text
2. add exact Transforms.removeText(editor, text, { at? })
3. rebase selection inward after the removal

That means the helper removes the exact text payload at one point. It does not claim:

• word/line/block deletion
• reverse deletion
• hanging deletion
• selection-spanning deletion

Reusable rule

For Slate v2 text removal:

• ship the exact low-level op first
• make the helper match the real op semantics
• rebase the current selection inward so cursor and range movement stay consistent with the underlying removal
• do not name broad deletion behavior as shipped until the engine really owns it

If the helper is broader than the real operation, the API is doing marketing, not engineering.