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.

bin/agenthub.js

@@ -4321,7 +4321,7 @@ async function cmdCodexAccounts(sub, name, flags) {
  * `agenthub accounts pin <account> <user>` / `unpin <user>` [--tool codex] —
  * that user's new sessions run on that account (server/lib/account-pins.js).
  */
-function cmdAccountPin(sub, positional, tool) {
+async function cmdAccountPin(sub, positional, tool) {
   const pins = require(path.join(REPO_ROOT, "server", "lib", "account-pins.js"));
   const [first, second] = positional;
   const username = sub === "pin" ? second : first;
@@ -4333,17 +4333,28 @@ function cmdAccountPin(sub, positional, tool) {
     .get(username);
   if (!user) throw new Error(`no user ${username}`);
   const pin = pins.setPin(user.id, tool, sub === "pin" ? first : null);
-  console.log(
-    pin.account
-      ? `${c.green("✔")} ${pin.username}'s new ${tool} sessions run on ${pin.account}`
-      : `${c.green("✔")} ${pin.username} unpinned — new ${tool} sessions use the balancer`
-  );
   if (!require(path.join(REPO_ROOT, "server", "lib", "auth.js")).isServerMode()) {
     console.log(c.dim("  Pins apply in server mode only."));
   }
-  console.log(c.dim("  Running sessions keep their account until they end."));
+  if (!pin.account) {
+    console.log(`${c.green("✔")} ${pin.username} unpinned — new ${tool} sessions use the balancer`);
+    return;
+  }
+  const switched = await pins.applyPin(user.id, tool);
+  console.log(`${c.green("✔")} ${pin.username}'s ${tool} sessions run on ${pin.account}`);
+  console.log(c.dim(`  ${SWITCH_NOTE[switched] || SWITCH_NOTE["next-session"]}`));
 }
 
+/** What `applyPin` did, for the CLI. */
+const SWITCH_NOTE = {
+  switched: "Switched now: running sessions take it at their next login check, new ones at once.",
+  kept: "Their home already holds it.",
+  "own-login":
+    "They signed in with their own login, which is left alone: no pool login is written over it.",
+  expired: "That login has expired: new sessions fall back to the balancer until it is re-added.",
+  "next-session": "New sessions use it; running ones keep their account until they end.",
+};
+
 /** The `pinned` column: who an admin pinned to `account`. */
 function pinnedUsers(tool, account) {
   try {