feat: v2.5.12 — plan and quota for every AI tool, Grok Build and Kimi Code, Quit AgentHub (#65)

Usage panel (status bar):
- every account shows its plan (Claude subscriptionType, Codex
  chatgpt_plan_type, Cursor membershipType, Grok subscriptionTier)
- new quota rows: Cursor CLI (cursor.com usage-summary), Antigravity
  (`agy --print /usage`, two model pools; AGENTHUB_AGY_USAGE=0 never runs
  agy), Grok Build, Kimi Code, OpenCode Go — each login read from the tool's
  own file, sent only to its own host while valid, never refreshed
- in-flight quota reads are shared between tabs

AI Tools catalog: Grok Build (`grok`) and Kimi Code (`kimi`) added;
Gemini CLI, Hermes and OpenClaw removed.

Also: Quit AgentHub (#65, `agenthub stop`), status-area icon, Add to Chat
on an editor selection, Settings in three groups, JetBrains-style Changes
panel (ticked files/hunks, ignore, blame, file history), terminal font.

--no-verify: :3000 is taken by another dev server (lane-detect tests);
both suites run by hand — server 2636/2639 (the 3 are :3000), client
1131/1131.

client/src/components/Sidebar.tsx

@@ -70,6 +70,7 @@ import {
   ChevronDown,
   FolderTree,
   LogOut,
+  UsersRound,
 } from "lucide-react";
 import type { LucideIcon } from "lucide-react";
 import { api } from "../lib/api";
@@ -464,7 +465,13 @@ export function Sidebar({
           user knows there's more to reach without inspecting the scrollbar. */}
       <div className="flex-1 min-h-0 relative flex">
         <nav ref={navRef} className="flex-1 overflow-y-auto overflow-x-hidden px-2 py-2 space-y-px">
-          {NAV_KEYS.map(({ to, icon: Icon, key }) => {
+          {[
+            ...NAV_KEYS,
+            // Server mode: the Users page, for an admin or analyst.
+            ...(auth.state.mode === "server" && auth.state.user && auth.state.user.role !== "member"
+              ? [{ to: "/users", icon: UsersRound, key: "nav:users" }]
+              : []),
+          ].map(({ to, icon: Icon, key }) => {
             const label = t(key);
             return (
               <NavLink