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.

README.en.md

@@ -48,6 +48,10 @@ open it in the browser and you are done.
 
 Something wrong? Send `/agenthub:agenthub-doctor` to check and fix it.
 To update to a new version: `/agenthub:agenthub-update`.
+Not using it? Quit so nothing runs in the background: **Settings → System → Quit**,
+or `agenthub stop` — opening Claude Code no longer starts it; `agenthub start` does.
+AgentHub's icon beside the clock (top bar / menu bar / notification area) offers
+**Open**, **Quit** and **Start AgentHub** too; hide it from its menu or in **Settings → System**.
 
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