feat: choose your own pool account; skills with "token" in a doc name upload; System Health off Linux

- Skill snapshot/upload: a key file's name (.env, *.pem, id_rsa, .netrc,
  .credentials.json…) is always refused, but a word like token/secret/
  password/credential only in a data file's name — design-tokens.md or
  count_tokens.py is skill content, not a key.
- System Health: off Linux the History, CPU threads and Busiest processes
  cards (all read from /proc) are left out instead of shown empty; the CPU
  bar without a sample and Windows' always-zero Load row go too.
- Users pick their own pool account per tool (/api/me/pool-accounts,
  Settings → AI tools), within their groups, refused while pinned.
- Admin user detail, 9router update, session replay and Antigravity
  catalog changes from parallel sessions.

client/src/components/settings/NineRouterUpdate.tsx

@@ -1,6 +1,6 @@
 /**
  * @file NineRouterUpdate.tsx
- * @description **Update 9router** on the AI Proxy page (an admin's; beside
+ * @description **Update 9router** on the AI Proxy page (every user's; beside
  * Config 9router): a button — dotted when npm has a newer 9router — and a
  * dialog that runs the server's three-step job (`server/lib/nine-router-update.js`):
  * disconnect and shut 9router down, `npm install -g 9router@latest`, start it