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.

docs/SERVER-MODE.md

@@ -109,7 +109,11 @@ start (`server/db.js`), and `member` is no longer accepted.
 `/api/settings`, `/updates`, `/codex-config`,
 `/git-credentials`, `/ai-tools`, `/import`, `/pricing`, `/budgets`,
 `/webhooks`, `/remote-sources`, `/reports`, `/pets`, `/users` and
-`/alerts/rules` (`ADMIN_WRITE_PREFIXES` in `server/lib/auth.js`), plus a write
+`/alerts/rules` (`ADMIN_WRITE_PREFIXES` in `server/lib/auth.js`) — except
+the two update buttons any signed-in user may press, `POST
+/api/ai-tools/update-all` and `POST /api/ai-proxies/9router/update`
+(`MEMBER_WRITE_EXCEPTIONS`; both run only what the catalog / the fixed 9router
+job names) — plus a write
 to a shared AI Proxy (see [AI Proxy profiles](#ai-proxy-profiles)) and the
 host-wide parts of `/cc-config` (see
 [Your own Claude Code config](#your-own-claude-code-config)). A
@@ -609,6 +613,27 @@ by team (Users page → **Account pool → Groups**, server mode only,
   an account takes it out of every group; deleting a group sends its members
   back to the shared pool and removes no account.
 
+### A user's own pool account
+
+When the pool holds more than one account a user may use, they pick which one
+their own new sessions run on: **Settings → AI tools → Pool account**, one
+select per tool (Claude, Codex, Cursor), every role, server mode only
+(`GET/PUT /api/me/pool-accounts`, `account_choices`, `server/lib/account-pins.js`).
+
+- The list is only what their group allows (or the shared pool); a choice
+  outside it is refused (`ENOACCOUNT`), and one later taken from the group
+  falls back to the balancer.
+- **Automatic** (the default) leaves it to the balancer.
+- An admin's pin wins and locks the select (`ELOCKED`); the choice comes back
+  once the pin is removed.
+- A Claude login goes into the user's home at once, like an admin's switch,
+  so running panes follow it; Codex and Cursor take it at the next session (a
+  ChatGPT login still waits while another holds the home).
+- It is the user's own change: the login cookie only (a pane token cannot),
+  audited, no password step-up. The Users page's user detail shows it as
+  "chose <account>". Oh My Pi has no pool to choose from (its sharing is the
+  host's one login).
+
 The tab bar also shows Oh My Pi (its login sharing, below) and every other
 installed tool, which says it has no pool (Antigravity keeps its Google login
 in the system keyring; there is no key AgentHub could hand a session).