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/routes/accounts.js

@@ -17,8 +17,9 @@
  * Keychain item's JSON); or `token` — a `claude setup-token` token. A Codex
  * one is an OpenAI API key or the text of an `auth.json` (`token`).
  * `PUT /pins` (`{tool, userId, account}`, `account: null` unpins) pins one
- * user's new sessions of a tool to one pool account (account-pins.js); `GET /`
- * lists the pins under `pins`.
+ * user's sessions of a tool to one pool account (account-pins.js) — a Claude
+ * login goes into their home at once, so running panes move without a
+ * restart (`switched`); `GET /` lists the pins under `pins`.
  * `GET /profiles` lists the saved profiles that can be moved in (identity only). Like every Users-page change
  * they need the admin's own password again (`currentPassword`), are audited
  * (the account NAME only), and refuse in local mode. The secret only goes IN:
@@ -213,10 +214,19 @@ router.post(
 
 router.put(
   "/pins",
-  poolChange((_req, body) => {
+  poolChange(async (_req, body) => {
     const pin = pins.setPin(Number(body.userId), body.tool, body.account ?? null);
+    let switched = null;
+    if (pin.account) {
+      try {
+        switched = await pins.applyPin(pin.userId, body.tool);
+      } catch (e) {
+        console.warn(`[accounts] switch ${pin.username} → ${pin.account}: ${e.message}`);
+        switched = "next-session";
+      }
+    }
     return {
-      json: { pin },
+      json: { pin, switched },
       target: pin.userId,
       action: pin.account
         ? `pool: pin ${pin.username} to ${body.tool} account ${pin.account}`