docs(20): UI design contract

.planning/phases/20-admin-member-editor-form-declutter/20-UI-SPEC.md

@@ -86,7 +86,7 @@ Accent (`--color-member-0`) reserved for:
 Accent is NOT used on:
 - Cancel buttons (use `--color-text-secondary`, no background)
 - Disabled buttons (use `--color-border` as background)
-- The "Add member" trigger button (use `--color-member-0` background — it is the primary CTA for the panel)
+- The "Add member" trigger button (ghost button: `--color-surface` background, `--color-surface-dim` hover — matches Surface A; not an accent CTA)
 - The row chevron/edit icon (use `--color-text-muted`)
 
 Member avatar swatches use `--color-member-{colorIndex}` (index-derived, unchanged from existing MemberRow).