Slate v2 Normalization Docs Truth Pass

Goal

Stop the normalization docs from implying full legacy built-in constraint parity when that family is still an open risky lane in slate-v2.

Completed

• updated docs/concepts/11-normalizing.md to distinguish:
  • the real current custom normalization seam
  • the still-open built-in normalization parity family
• updated docs/concepts/02-nodes.md to remove the implied guarantee that inline spacing is automatically restored by built-in normalization

Verification

• targeted grep over the touched docs for the new normalization warning language
• yarn lint:typescript