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.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "agenthub",
-  "version": "2.5.11",
+  "version": "2.5.12",
   "bin": {
     "agenthub": "bin/agenthub.js"
   },
@@ -79,6 +79,7 @@
     "multer": "^2.0.0",
     "redoc": "^2.5.3",
     "swagger-ui-express": "^5.0.1",
+    "systray2": "^2.1.4",
     "tar": "^7.4.3",
     "uuid": "^11.1.0",
     "web-push": "^3.6.7",