Header: show Civi stage label prominently; restore current_stage readonly in Stage 0

- New STAGE_OPTION_GROUP_ID constant (=75) added to config and consumed
  by both the in-card readonly and the header. Because the field carries
  optionGroupId, /api/data auto-includes the Stage option group in its
  parallel fetch (via the existing optionGroupIds derivation).
- SubmissionContextHeader: dropped the small inline 'Stage Organizing'
  line. Replaced with an uppercase 'Current stage' eyebrow next to the
  progress dots, followed by a display-font 20/24px leaf-toned label
  underneath. Resolves the stored option value ('Organizing') to its
  Civi option label ('Stage 1 — Convene & Prepare') via the new
  resolveStageLabel helper; falls back to the raw value if the option
  group hasn't loaded.
- Stage 0 'Check-in (organizing)' section: re-added a current_stage
  readonly field at the top. With optionGroupId set, FieldRenderer's
  readonly branch resolves the value to the Civi label for display.

config/form.ts

@@ -34,6 +34,13 @@ const visibleAtOrAfter = (...stages: string[]): VisibilityRule => ({
   values: stages,
 });
 
+/**
+ * Option group ID for the `Stage` option group on `client.crm.fci.coop`.
+ * Used to resolve the current stage value (e.g. "Organizing") to its Civi
+ * label (e.g. "Stage 1 — Convene & Prepare") for display.
+ */
+export const STAGE_OPTION_GROUP_ID = 75;
+
 // CiviCRM custom group machine names per the APIv4 inventory.
 const G0 = "Check_in_data__organizing_";
 const G1 = "Stage_1";
@@ -50,10 +57,18 @@ const stage0: StageSectionConfig = {
   intro:
     "Core check-in fields. These are visible at every stage and capture the data we follow over time across the lifecycle of the co-op.",
   fields: [
-    // `current_stage` is still tracked in form state (it gates every Stage
-    // 1–5 visibleWhen rule and feeds the journey rail), but it is no longer
-    // rendered as an in-card field — the SubmissionContextHeader displays
-    // the activity-derived Stage value as readonly above the cards.
+    // current_stage is a UI-only readonly field. Its value is the Civi
+    // option *value* (e.g. "Organizing") sourced by /api/data from the
+    // most recent stage-bearing Check-in (organizing) activity. Setting
+    // `optionGroupId` makes the readonly renderer resolve the value to
+    // its Civi option *label* (e.g. "Stage 1 — Convene & Prepare") for
+    // display. The form never writes Stage back to the activity.
+    {
+      name: "current_stage",
+      label: "Current stage",
+      type: "readonly",
+      optionGroupId: STAGE_OPTION_GROUP_ID,
+    },
     {
       name: "Peer_Group_Participation",
       label: "Peer Group Participation",