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/__tests__/claude-pool-login.test.js

@@ -10,7 +10,8 @@
  * Users-page route moves a saved switch-user profile in — the one this
  * machine's own Claude Code is logged into with its LIVE login, the host's
  * home then being one more placement the server refreshes. A pin of the
- * owner to another login waits while a live pane holds the first.
+ * owner to another login waits while a live pane holds the first, until the
+ * admin's switch writes it into the home (never over the member's own login).
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -189,7 +190,7 @@ describe("a pool login", () => {
     assert.equal(pool.__read("team"), null);
   });
 
-  it("follows the owner's pin, but never over another login a live pane holds", () => {
+  it("follows the owner's pin, and an admin's switch moves the home's login now", async () => {
     const { db } = require("../db");
     const pins = require("../lib/account-pins");
     const miaId = db.prepare("SELECT id FROM users WHERE username = 'mia'").get().id;
@@ -212,9 +213,22 @@ describe("a pool login", () => {
       `INSERT INTO dashboard_runs (id, mode, cwd, status, started_at, account, lane_id, tool)
        VALUES ('pin-run', 'interactive', ?, 'running', ?, 'alpha', ?, 'claude')`
     ).run(path.join(HOME, "proj"), new Date().toISOString(), lane);
-    assert.equal(pool.forSpawn(acct, miaId).name, "alpha");
-    db.prepare("UPDATE dashboard_runs SET status = 'completed' WHERE id = 'pin-run'").run();
+    assert.equal(pool.forSpawn(acct, miaId).name, "alpha", "a bare pin waits for the pane");
+    // The admin's switch writes beta into the home now; the pane is not touched.
+    assert.equal(await pins.applyPin(miaId, "claude"), "switched");
+    assert.equal(diskCreds().refreshToken, oauth("b").refreshToken);
+    assert.equal(pool.__read("alpha").placed.mia, undefined, "alpha no longer holds mia's home");
     assert.equal(pool.forSpawn(acct, miaId).name, "beta");
+    assert.equal(await pins.applyPin(miaId, "claude"), "kept");
+    // Unpinned with the pane still live: the home's login stays, no flip back.
+    pins.setPin(miaId, "claude", null);
+    assert.equal(pool.forSpawn(acct, miaId).name, "beta");
+    // A login the member made themselves is never written over.
+    fs.writeFileSync(CREDS, JSON.stringify({ claudeAiOauth: oauth("own") }));
+    pins.setPin(miaId, "claude", "alpha");
+    assert.equal(await pins.applyPin(miaId, "claude"), "own-login");
+    assert.equal(diskCreds().refreshToken, oauth("own").refreshToken);
+    pins.setPin(miaId, "claude", "beta");
     pool.removeAccount("beta");
     assert.equal(pins.pinFor(miaId, "claude"), null, "a removed account drops its pins");
     db.prepare("DELETE FROM dashboard_runs WHERE id = 'pin-run'").run();