fix(webapp): lock the per-organisation snapshot dial on the global flags page

The per-organisation dial is read from the organisation blob only, and a global
save refuses it outright, but the global page still rendered an editable control
for it. The only outcome of using that control was a rejected save. It now
renders read-only, matching every other organisation-scoped flag.

Author: d-cs

apps/webapp/app/v3/featureFlags.ts

@@ -181,6 +181,9 @@ export const GLOBAL_LOCKED_FLAGS: FeatureFlagKey[] = [
   FEATURE_FLAG.runOpsMintKindFlippedAt,
   FEATURE_FLAG.runOpsMintShardSetPrev,
   FEATURE_FLAG.runOpsMintShardSetFlippedAt,
+  // Read from the org blob only, and refused outright on a global save, so an editable control here
+  // would offer a setting whose only outcome is a 400.
+  FEATURE_FLAG.snapshotStoreOrgMode,
 ];
 
 // Flags that are read-only on the org-level dialog.

apps/webapp/test/snapshotStoreFlagGuard.test.ts

@@ -3,6 +3,7 @@ import {
   globalOnlySnapshotStoreFlagError,
   snapshotStoreFlagSaveError,
 } from "~/v3/snapshotStoreFlagGuard.server";
+import { FEATURE_FLAG, GLOBAL_LOCKED_FLAGS } from "~/v3/featureFlags";
 
 describe("snapshotStoreFlagSaveError", () => {
   it("refuses a flip past off when no host is configured", () => {
@@ -80,3 +81,19 @@ describe("globalOnlySnapshotStoreFlagError", () => {
     expect(globalOnlySnapshotStoreFlagError({ runOpsMintKind: "cuid" })).toBeUndefined();
   });
 });
+
+describe("the global page and the save guard agree", () => {
+  it("locks every flag the global save path refuses", () => {
+    // A flag the guard rejects but the page leaves editable renders a control whose only outcome is
+    // a 400. The convention above GLOBAL_LOCKED_FLAGS states this; the assertion enforces it.
+    for (const key of [FEATURE_FLAG.snapshotStoreOrgMode] as const) {
+      expect(globalOnlySnapshotStoreFlagError({ [key]: "dual-write" })).toBeDefined();
+      expect(GLOBAL_LOCKED_FLAGS).toContain(key);
+    }
+  });
+
+  it("leaves the deployment-wide dial editable on the global page", () => {
+    expect(globalOnlySnapshotStoreFlagError({ snapshotStoreMode: "dual-write" })).toBeUndefined();
+    expect(GLOBAL_LOCKED_FLAGS).not.toContain(FEATURE_FLAG.snapshotStoreMode);
+  });
+});