test(sharing): admit the switch endpoint to the actor-surface list

The first entry in either frozen list. It is the way back out of a
switch: every other route refuses while one is active, so a browser that
could not reach this one would be stuck inside a record it entered. The
entry names why it may say what it says — one session row, the caller's
own, nothing of the owner's rendered and nothing granted.

The entry count moves with it, so an addition has to be made twice
rather than once.

src/__tests__/delegable-surface-guard.test.ts

@@ -250,21 +250,23 @@ const DELEGABLE_ROUTES: Record<string, string> = {};
  * switch, because they serve the caller's own account and nothing of the
  * owner's.
  *
- * Also empty today, and for the same reason: the resolver exists, its members
- * do not yet. The intended first five — the account bootstrap payload, the
- * switch endpoint itself, logout, the native refresh route, and the locale
- * read — are the surfaces a switched session needs in order to stay usable and
- * to switch back. None of them exists in this shape yet, and naming them here
- * before they do would freeze a guess.
+ * The intended members are the surfaces a switched session needs in order to
+ * stay usable and to get back out: the account bootstrap payload, the switch
+ * endpoint, logout, the native refresh route, the locale read. One of them
+ * exists so far. The rest arrive as their own diffs here; naming them before
+ * they exist would freeze a guess.
  */
-const ACTOR_ROUTES: Record<string, string> = {};
+const ACTOR_ROUTES: Record<string, string> = {
+  "app/api/account/switch/route.ts":
+    "The way back out. Every other route refuses under a switch, so if this one did too a browser could enter a record and never leave it. It reads and writes exactly one row — the caller's own session — renders nothing of the owner's, and grants nothing: the account it stamps is validated against a live grant first, and the stamp is re-checked on every request after.",
+};
 
 /**
  * Entries across both lists. Pinned so that the reason-loop below cannot stay
- * a formality by accident: it runs zero times today, and the day it stops
- * running zero times somebody has to say so here.
+ * a formality by accident: every addition has to be counted here as well as
+ * listed above, which is one more place a careless admission has to pass.
  */
-const FROZEN_ENTRY_COUNT = 0;
+const FROZEN_ENTRY_COUNT = 1;
 
 /**
  * The two surfaces that authenticate a Bearer token outside `requireAuth` —
@@ -502,10 +504,8 @@ describe("every frozen entry carries a reason", () => {
       expect(reason.trim().length, `${rel} has no reason`).toBeGreaterThan(0);
     }
 
-    // Both lists are empty, so the loop above runs zero times and proves
-    // nothing today. Said out loud rather than left to be discovered: this
-    // count is what forces the next person adding an entry to notice that the
-    // reason check has been dormant.
+    // The loop above now runs, once. The count stays because it is what makes
+    // an addition visible twice — in the list and here — rather than once.
     expect(entries.length).toBe(FROZEN_ENTRY_COUNT);
   });
 });