Restore thin scalar inline-edit helper (formerly useEditable)

[developer-1px]

Context

zod-admin-ui (https://github.com/developer-1px/zod-admin-ui) used useEditable<T>({ getValue, onCommit }) from @p/anyeditable v0.4.x for scalar inline editing — the double-click-to-edit pattern over a single string value backed by a zod-crud RFC 6902 pointer.

After v0.5 migration to block-based composer, useEditable no longer exports. The new useEditableSurface / useEditableDocumentSurface operate over ComposerDoc (multi-block document) — overkill for a single scalar that lives at a JSON Pointer in an external doc.

Missing surface

useEditable<Id>({
  getValue: (id) => string,
  onCommit: (id, next: string) => void,
}): {
  editing: Id | null
  inputProps: React.InputHTMLAttributes<HTMLInputElement>  // onBlur=commit, Enter=commit, Esc=cancel
  startEdit: (id: Id) => void
}

Why thin shape matters

For NCloud-style admin we have hundreds of leaf strings (headline, eyebrow, button labels) edited inline within a preview tree. Each leaf is one JSON pointer of an external doc — not a block document. Spinning up useEditableSurface per leaf is wrong layer.

Asks

1. Restore (or add) a thin useEditable scalar helper alongside the block surface.
2. Or document the canonical pattern for "edit one string at a JSON pointer" in admin context.

Impacted consumer code

• src/auto/preview/inline-edit/EditableText.tsx
• src/auto/preview/inline-edit/useDocEditable.ts

We are using a local thin replacement until this surface returns.