feat(pool): an admin's switch moves a user's Claude login at once

PUT /api/accounts/pins (and agenthub accounts pin) now writes a pinned
Claude login into the user's home right away (claude-pool.switchHome):
every home's newer pair is copied back first, the member's own login is
never written over, and no pane is restarted — running sessions take the
new pair at their next credentials read. A live home stays on the login it
holds, so unpinning does not flip it back. The Users page calls it
"Switch a user's account" and says what happened.

server/openapi-extra/auth.js

@@ -731,7 +731,7 @@ const paths = {
       tags: ["Auth"],
       operationId: "pinPoolAccount",
       summary:
-        "Admin: pin one user's new sessions of a tool to one pool account (`account: null` unpins), with their own password again",
+        "Admin: switch one user's sessions of a tool to one pool account (`account: null` = automatic), with their own password again. A Claude login is written into their home at once; running panes take it without a restart",
       requestBody: {
         required: true,
         content: {
@@ -750,7 +750,10 @@ const paths = {
         },
       },
       responses: {
-        200: { description: "`{pin: {userId, username, account}}` — `account` null when unpinned" },
+        200: {
+          description:
+            "`{pin: {userId, username, account}, switched}` — `account` null when unpinned; `switched`: switched | kept | own-login | expired | next-session | null",
+        },
         400: err("EBADTOOL"),
         403: err("EREAUTH — wrong password; EADMIN — not an admin; ELOCALMODE"),
         404: err("ENOUSER, ENOACCOUNT"),