feat(pool): one board of pools with split/merge by drag; plan names from tier and seat

- The Users page account pool is one board: a column per pool holding its
  Claude Code, Codex and Cursor accounts (plan, quota, live panes) and its
  members. Accounts sit in one pool; drag moves them. Drop on New pool to
  split one off; drag a pool's only account into another pool to merge
  (members follow, the emptied pool is deleted on Save). One password Save.
- Claude plan label (planLabel in cc-profiles.js) reads rateLimitTier and
  seatTier: Max 5x/20x, Team Standard/Premium — subscriptionType alone said
  'pro' after an upgrade and 'team' for both seats. Shown on profiles, the
  status bar quota badge and pool cards; Codex pool cards show the ChatGPT plan.

client/src/components/settings/ToolProfilesSettings.tsx

@@ -800,7 +800,7 @@ function ProfileUsageLine({
 
 /** Org / seat / plan line shared by the active card and each profile row. */
 function IdentityLine({ identity }: { identity: CcAccountIdentity }) {
-  const parts = [identity.organization, identity.seatTier, identity.subscriptionType].filter(
+  const parts = [identity.organization, identity.plan || identity.subscriptionType].filter(
     Boolean
   );
   if (parts.length === 0) return null;