Remove contact identity fields from Stage 0 and widen Current stage

Drop the readonly First name, Last name, and Email fields from the
Check-in (organizing) section display. Add an optional fullWidth flag to
FieldConfig and set it on current_stage so it spans the full section grid.

config/form.ts

@@ -103,24 +103,7 @@ const stage0: StageSectionConfig = {
       label: "Current stage",
       type: "readonly",
       optionGroupId: STAGE_OPTION_GROUP_ID,
-    },
-    // Contact identity, sourced from the cid in /api/data. Display-only —
-    // never written back to Civi. These confirm to the form-filler which
-    // contact record their submission will be attributed to.
-    {
-      name: "contact_first_name",
-      label: "First name",
-      type: "readonly",
-    },
-    {
-      name: "contact_last_name",
-      label: "Last name",
-      type: "readonly",
-    },
-    {
-      name: "contact_email",
-      label: "Email",
-      type: "readonly",
+      fullWidth: true,
     },
     // Org-contact fields (Food_Co_op_Organizing custom group). These live
     // on the Organization Contact record, not on the Check-in activity, so