Derive current stage from most-recent stage-bearing activity

Stage authority moves from Organization.Food_Co_op_Organizing.Stage to the
most recent Check-in (organizing) activity whose Stage custom field is set.
Staff create these activities manually to mark transitions; org-owner form
submissions no longer write the Stage field at all, so they cannot override
a staff-set transition.

- /api/data: removed the Contact.get for org-side Stage; added an
  Activity.get filtered to ACTIVITY_TYPE_NAME + ACTIVITY_STAGE_FIELD IS
  NOT EMPTY, ordered by activity_date_time DESC, id DESC, limit 1.
  Fallback when no such activity exists: Inquiry (rank 0). Org-name
  lookup, stage activity, prefill, and option-group fetch all run in
  parallel via Promise.all.
- /api/submit: removed the stageAtSubmission read + the
  [ACTIVITY_STAGE_FIELD] write on the activity record. The form's
  activities are stage-null by design now.
- config/form.ts: dropped the stage_at_submission readonly field (no
  longer being set or displayed). Kept ACTIVITY_STAGE_FIELD export — it's
  now used by /api/data to find stage-bearing activities. Updated the
  current_stage field comment to reflect the new source.
- components/EngagementForm.tsx: dropped stage_at_submission from
  evalState (no longer referenced by any visibility rule or readonly
  display).

Org.Food_Co_op_Organizing.Stage remains in CiviCRM for staff list views;
the middleware no longer reads or writes it. No backfill required —
orgs without a stage-bearing activity simply read as Inquiry.

app/api/submit/route.ts

@@ -5,16 +5,17 @@
  *
  * Verifies checksum, resolves org from cid (mirror of /api/data), then
  * creates a new `Check-in (organizing)` activity. The activity's own Stage
- * field (`Check_in_data__organizing_.Stage`) is auto-populated from the
- * org's current `Food_Co_op_Organizing.Stage` so each check-in carries a
- * snapshot of where the org was at submission time.
+ * field is intentionally left null: the form is not the authority on stage.
+ * Staff set Stage on their own check-in activities to mark transitions, and
+ * /api/data derives the org's current stage from the most recent stage-
+ * bearing activity.
  *
  * STUB MODE: if CiviCRM env vars are unset, returns success without writing.
  */
 
 import { NextResponse } from "next/server";
 import { civi, verifyChecksum } from "@/lib/civicrm";
-import { allFields, ACTIVITY_TYPE_NAME, ACTIVITY_STAGE_FIELD, FORM_CONTACT_RELATIONSHIP } from "@/config/form";
+import { allFields, ACTIVITY_TYPE_NAME, FORM_CONTACT_RELATIONSHIP } from "@/config/form";
 import type { SubmitPayload } from "@/types/form";
 import { appEnv, redact } from "@/lib/env";
 import { rateLimit, clientIp } from "@/lib/rate-limit";
@@ -102,33 +103,19 @@ async function runSubmit(cid: string, cs: string, values: Record<string, unknown
   }
   const orgId = orgs[0].contact_id_b;
 
-  // Read the org's current Framework Stage so we can snapshot it on the activity.
-  const orgRes = await civi<{ "Food_Co_op_Organizing.Stage": string | null }>(
-    "Contact",
-    "get",
-    {
-      select: ["Food_Co_op_Organizing.Stage"],
-      where: [["id", "=", orgId]],
-    },
-  );
-  const stageAtSubmission = orgRes.values?.[0]?.["Food_Co_op_Organizing.Stage"] ?? null;
-
-  // Build the activity record. Each form-side field name maps to its
-  // configured `civiField` for the activity-side write.
+  // Build the activity record. The Stage custom field is deliberately NOT
+  // set here — staff own stage transitions on their own activities.
   const activityRecord: Record<string, unknown> = {
     "activity_type_id:name": ACTIVITY_TYPE_NAME,
     "status_id:name": "Completed",
     target_contact_id: orgId,
     source_contact_id: Number(cid),
     subject: "Co-op Check-in (form submission)",
-    [ACTIVITY_STAGE_FIELD]: stageAtSubmission,
   };
   for (const [name, value] of Object.entries(values)) {
     const field = FIELD_BY_NAME.get(name);
     if (!field || !field.civiField) continue;
     if (field.type === "readonly") continue; // never write read-only fields
-    if (name === "current_stage") continue; // org-side, never written to activity
-    if (name === "stage_at_submission") continue; // handled above via ACTIVITY_STAGE_FIELD
     activityRecord[field.civiField] = value;
   }