Add field access checks before activating editable elements

[formfcw]

Scope

What's changed:

• Editable elements now go through a two-phase lifecycle: lightweight construction → activate() (overlay, observers, listeners) only after permission check
• apply() sends a checkFieldAccess message to the parent Directus frame with collection/item/fields for each new element
• Parent responds with activateElements containing keys of permitted elements — only those get activated
• New types: CheckFieldAccessData, new actions: checkFieldAccess (send) / activateElements (receive)

Potential Risks / Drawbacks

• Breaking change: elements won't show edit overlays unless the parent frame responds to checkFieldAccess with activateElements — requires Directus
  v11.16.0+
• This might warrant bumping to v2.0.0 given the breaking nature

Review Notes / Questions

• This PR is related to vev ← Add field permission and version access checks to Visual Editor directus#26749
• Should this be released as v2.0.0 due to the breaking change, or is documenting the minimum Directus version in the README sufficient?
• Elements that fail the permission check remain inert (no overlay, no hover listeners, no rect observation) — they stay registered in the store but are never visible
  to the user

[robluton]

LGTM 🎸