Revert "feat(topics): add the Topics preview area, its navigation entry and its switch"

This reverts commit c68e833dcc.

src/__tests__/baselines/test-as-never.json

@@ -1,7 +1,7 @@
 {
   "$comment": "as never casts in tests, per test file under src/. Maintained by src/__tests__/test-realism-ratchet.test.ts.",
-  "count": 523,
-  "total": 5494,
+  "count": 524,
+  "total": 5495,
   "entries": {
     "__tests__/api/auth/login/mfa-branch.test.ts": 10,
     "__tests__/api/auth/mfa/verify.test.ts": 9,
@@ -273,6 +273,7 @@
     "components/medications/__tests__/use-medication-intake.test.ts": 1,
     "components/medications/detail/efficacy/__tests__/change-at-start-summary.test.tsx": 1,
     "components/mood/__tests__/mood-list-url-sync.test.tsx": 1,
+    "components/settings/__tests__/settings-shell.test.tsx": 1,
     "components/settings/integrations/__tests__/dawarich-card.test.tsx": 1,
     "components/timeline/__tests__/medication-rows.test.ts": 1,
     "lib/__tests__/acting-account-resolver.test.ts": 5,

src/__tests__/baselines/version-stamp-comments.json

@@ -1,7 +1,7 @@
 {
   "$comment": "Comment lines that open with a release version, per file under src/. Maintained by src/__tests__/version-stamp-ratchet.test.ts.",
   "count": 2954,
-  "total": 10499,
+  "total": 10500,
   "entries": {
     "__tests__/account-payload-consumer-guard.test.ts": 2,
     "__tests__/acting-account-boundary-guard.test.ts": 7,
@@ -2807,7 +2807,7 @@
     "lib/rollups/mood-rollups.ts": 4,
     "lib/rollups/tiered-context.ts": 6,
     "lib/score-config/rows.ts": 1,
-    "lib/settings/section-slugs.ts": 19,
+    "lib/settings/section-slugs.ts": 20,
     "lib/sharing/__tests__/account-access-parse.test.ts": 3,
     "lib/sharing/__tests__/account-access.test.ts": 2,
     "lib/sharing/__tests__/account-label.test.ts": 1,

src/__tests__/settings-copy-tense.test.ts

@@ -3,9 +3,8 @@
  *
  * The workout-route switch is off for new accounts, which is what its detail
  * says rather than "off by default": an account that already held tracks at
- * the upgrade started with it on (migration 0434). The Topics preview switch
- * this file also held describes pages that now exist, so its copy is in the
- * present tense like every other switch.
+ * the upgrade started with it on (migration 0434). (The Topics preview switch
+ * this file also held is unlisted until its pages ship, and its copy with it.)
  */
 import { describe, expect, it } from "vitest";
 

src/__tests__/settings-legacy-routes.test.ts

@@ -54,8 +54,6 @@ const HISTORICAL_SETTINGS_PATHS: readonly string[] = [
   "/settings/export",
   "/settings/advanced",
   "/settings/privacy",
-  // Preview features (Settings > System).
-  "/settings/preview",
   "/settings/about",
   // The per-module personalisation slugs before the layout hub.
   "/settings/dashboard",