refactor(settings): remove the preview-feature opt-ins

The per-account preview switch was kept for the topic overview pages,
which were dropped before they shipped. Its one flag was stored, served
and backed up, and read by nothing; the column-reader audit listed it as
a pending consumer that will not come.

Removed completely:

- `/api/settings/preview-features` (GET, PATCH) is retired: it answers
  410 Gone with `meta.errorCode: route.retired` and `removedIn: 1.46.0`,
  and the contract publishes it under Retired. The route, its validation
  schema, the `PreviewFeatures` OpenAPI schemas and the settings module
  are deleted.
- Migration 0485 drops `users.preview_features_json` under a bounded lock
  wait, with the retry marker.
- The backup no longer writes the field. A file from v1.44 or v1.45 that
  carries it still restores: the schema accepts it and no codec reads it,
  so nothing is refused or written for it. The backup-parity goldens
  lose the field and apply one setting fewer.
- The data-wipe plan entry and the sharing-surface actor entry go with
  the route (frozen count 273 -> 272).

No client build reads the route: neither iOS repository nor any local
checkout references it.

tests/durations/unit.json

@@ -2660,7 +2660,6 @@
     "src/lib/search/__tests__/match.test.ts": 0,
     "src/lib/search/__tests__/search-records.test.ts": 0,
     "src/lib/settings/__tests__/module-list-layout.test.ts": 0,
-    "src/lib/settings/__tests__/preview-features.test.ts": 0,
     "src/lib/sharing/__tests__/account-access-parse.test.ts": 0,
     "src/lib/sharing/__tests__/account-access.test.ts": 0,
     "src/lib/sharing/__tests__/account-label.test.ts": 0,

tests/integration/__golden__/backup-parity/export-disaster-recovery.json

@@ -124,9 +124,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4
@@ -2566,9 +2563,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4

tests/integration/__golden__/backup-parity/export-portable.json

@@ -63,9 +63,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4
@@ -1725,9 +1722,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4

tests/integration/__golden__/backup-parity/restore-disaster-recovery-over-live.json

@@ -332,7 +332,7 @@
           "symptomDefinitions": 2,
           "lifeEvents": 3
         },
-        "accountSettingsApplied": 62,
+        "accountSettingsApplied": 61,
         "skipped": {
           "catalogueKeys": [],
           "links": 0

tests/integration/__golden__/backup-parity/restore-disaster-recovery.json

@@ -332,7 +332,7 @@
           "symptomDefinitions": 0,
           "lifeEvents": 0
         },
-        "accountSettingsApplied": 62,
+        "accountSettingsApplied": 61,
         "skipped": {
           "catalogueKeys": [],
           "links": 0
@@ -2759,9 +2759,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4
@@ -3029,9 +3026,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4

tests/integration/__golden__/backup-parity/restore-portable.json

@@ -378,7 +378,7 @@
           "symptomDefinitions": 0,
           "lifeEvents": 0
         },
-        "accountSettingsApplied": 62,
+        "accountSettingsApplied": 61,
         "skipped": {
           "catalogueKeys": [
             {
@@ -2254,9 +2254,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4
@@ -2463,9 +2460,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4

tests/integration/__golden__/backup-parity/restore-skips.json

@@ -894,7 +894,6 @@
       "documentsLayoutJson": null,
       "moodTagLayoutJson": null,
       "moduleListLayoutJson": null,
-      "previewFeaturesJson": null,
       "activityGoalsJson": null,
       "glucoseUnit": null,
       "hasDiabetes": false,

tests/integration/__golden__/backup-parity/restore-version-1.json

@@ -1027,7 +1027,6 @@
       "documentsLayoutJson": null,
       "moodTagLayoutJson": null,
       "moduleListLayoutJson": null,
-      "previewFeaturesJson": null,
       "activityGoalsJson": null,
       "glucoseUnit": null,
       "hasDiabetes": false,
@@ -1247,7 +1246,6 @@
       "moodTagLayoutJson": null,
       "documentsLayoutJson": null,
       "moduleListLayoutJson": null,
-      "previewFeaturesJson": null,
       "activityGoalsJson": null,
       "reportSelectionJson": null,
       "globalExcludedInjectionSites": [],

tests/integration/__golden__/backup-parity/seeded-account.json

@@ -2374,9 +2374,6 @@
       "moduleListLayoutJson": {
         "roundTrip": "rt-User-moduleListLayoutJson"
       },
-      "previewFeaturesJson": {
-        "roundTrip": "rt-User-previewFeaturesJson"
-      },
       "activityGoalsJson": {
         "stepsPerMonth": 250000,
         "workoutsPerWeek": 4

tests/integration/settings-prefs-routes.test.ts

@@ -1,13 +1,10 @@
 /**
- * The two per-user Settings preferences that live outside the account
- * payload, end to end against Postgres:
- *
- * - `/api/settings/module-list-layout`: defaults without a write, one list
- *   changed per PUT with preserve-when-absent fields and untouched neighbours,
- *   the multi-issue 422 for unknown values, and the column carrying only what
- *   was chosen.
- * - `/api/settings/preview-features`: all off by default, PATCH keeps the
- *   flags it does not name, an unknown flag or an empty body is refused.
+ * The per-user list layout, a Settings preference that lives outside the
+ * account payload, end to end against Postgres:
+ * `/api/settings/module-list-layout` answers defaults without a write,
+ * changes one list per PUT with preserve-when-absent fields and untouched
+ * neighbours, refuses unknown values with the multi-issue 422, and stores
+ * only what was chosen.
  */
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
@@ -173,51 +170,8 @@ describe("/api/settings/module-list-layout — integration", () => {
   });
 });
 
-describe("/api/settings/preview-features — integration", () => {
-  const URL = "http://localhost/api/settings/preview-features";
-
-  it("is all off by default and keeps a flag once switched on", async () => {
-    const { userId } = await seedUser();
-    const { GET, PATCH } =
-      await import("@/app/api/settings/preview-features/route");
-
-    const before = await (GET as Handler)(new Request(URL));
-    expect(((await before.json()) as { data: unknown }).data).toEqual({
-      topics: false,
-    });
-
-    const on = await (PATCH as Handler)(json("PATCH", URL, { topics: true }));
-    expect(on.status).toBe(200);
-    expect(((await on.json()) as { data: unknown }).data).toEqual({
-      topics: true,
-    });
-
-    const after = await (GET as Handler)(new Request(URL));
-    expect(((await after.json()) as { data: unknown }).data).toEqual({
-      topics: true,
-    });
-    const row = await getPrismaClient().user.findUnique({
-      where: { id: userId },
-      select: { previewFeaturesJson: true },
-    });
-    expect(row?.previewFeaturesJson).toEqual({ topics: true });
-  });
-
-  it("refuses an unknown flag and an empty body", async () => {
-    await seedUser();
-    const { PATCH } = await import("@/app/api/settings/preview-features/route");
-    const unknown = await (PATCH as Handler)(
-      json("PATCH", URL, { topics: true, darkMagic: true }),
-    );
-    expect(unknown.status).toBe(422);
-    const empty = await (PATCH as Handler)(json("PATCH", URL, {}));
-    expect(empty.status).toBe(422);
-  });
-});
-
 describe("settings presentation follows the person, also while acting for a record", () => {
   const LAYOUT = "http://localhost/api/settings/module-list-layout";
-  const PREVIEW = "http://localhost/api/settings/preview-features";
 
   async function actingForAnotherRecord() {
     const prisma = getPrismaClient();
@@ -251,10 +205,9 @@ describe("settings presentation follows the person, also while acting for a reco
     return { ownerId: owner.id, actorId: actor.id };
   }
 
-  it("reads and saves the actor's own layout and preview switch", async () => {
+  it("reads and saves the actor's own layout", async () => {
     const { ownerId, actorId } = await actingForAnotherRecord();
     const layout = await import("@/app/api/settings/module-list-layout/route");
-    const preview = await import("@/app/api/settings/preview-features/route");
 
     expect((await (layout.GET as Handler)(new Request(LAYOUT))).status).toBe(
       200,
@@ -263,20 +216,12 @@ describe("settings presentation follows the person, also while acting for a reco
       json("PUT", LAYOUT, { version: 1, list: "labs", view: "cards" }),
     );
     expect(put.status).toBe(200);
-    expect((await (preview.GET as Handler)(new Request(PREVIEW))).status).toBe(
-      200,
-    );
-    const patch = await (preview.PATCH as Handler)(
-      json("PATCH", PREVIEW, { topics: true }),
-    );
-    expect(patch.status).toBe(200);
 
     const rows = await getPrismaClient().user.findMany({
       where: { id: { in: [ownerId, actorId] } },
       select: {
         id: true,
         moduleListLayoutJson: true,
-        previewFeaturesJson: true,
       },
     });
     const actor = rows.find((r) => r.id === actorId)!;
@@ -284,9 +229,7 @@ describe("settings presentation follows the person, also while acting for a reco
     expect(actor.moduleListLayoutJson).toMatchObject({
       labs: { view: "cards" },
     });
-    expect(actor.previewFeaturesJson).toEqual({ topics: true });
     expect(owner.moduleListLayoutJson).toBeNull();
-    expect(owner.previewFeaturesJson).toBeNull();
   });
 });
 

tests/integration/settings-round-trip.test.ts

@@ -69,7 +69,6 @@ import * as medicationLayout from "@/app/api/medications/layout/route";
 import * as moodTagLayout from "@/app/api/mood/tags/layout/route";
 import * as documentsLayout from "@/app/api/documents/inbound/layout/route";
 import * as moduleListLayout from "@/app/api/settings/module-list-layout/route";
-import * as previewFeatures from "@/app/api/settings/preview-features/route";
 import * as activityGoals from "@/app/api/activity/goals/route";
 import * as healthKit from "@/app/api/integrations/healthkit/route";
 import { POST as exportHealthRecord } from "@/app/api/export/health-record/route";
@@ -888,21 +887,6 @@ function entries(user: Pick<User, "id">): Entry[] {
       },
       expected: ["list", "alphaAsc"],
     },
-    {
-      columns: ["previewFeaturesJson"],
-      write: {
-        handler: previewFeatures.PATCH,
-        method: "PATCH",
-        route: "/api/settings/preview-features",
-        body: { topics: true },
-      },
-      read: get(
-        previewFeatures.GET,
-        "/api/settings/preview-features",
-        "topics",
-      ),
-      expected: true,
-    },
     {
       columns: ["activityGoalsJson"],
       write: {