feat(server-s3): a member's tmux follows tmux upgrades — tmux-member + Users → Members' tmux

A member's tmux server keeps the version it started with until their last
pane closes, but the dashboard asked it with TMUX_BIN, the newest tmux: a
3.8 client on a 3.6 server spun it at 100% CPU (three members needed a
manual kill on 2026-10-15).

- /opt/agenthub/libexec/tmux-member (install-system, in sudoers): runs a
  member's tmux call with the binary of THEIR running server
  (/proc/<pid>/exe, found from the socket in /proc/net/unix), else
  TMUX_BIN. It runs as the member and execs only a process they own.
  sudoArgv uses it once installed (linux-accounts readConf), TMUX_BIN
  until then.
- Users → Members' tmux (GET /api/users/tmux): each member server's version
  beside the installed one, sessions, agents working. An admin restarts one
  (POST /api/users/:id/tmux-restart) or every idle outdated one
  (POST /api/users/tmux-restart-idle), with their password again, audited
  per member; a server that will not stop answers 409 ETMUXSTUCK naming
  its pid for root.
- server-s3-system.test.js: `delete` is a provision action since Delete
  user, so the "unknown action" case now uses `purge`.

Operators: run `sudo agenthub server install-system` once.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/openapi-extra/auth.js

@@ -14,6 +14,8 @@
  *   - GET/PUT/DELETE /api/me/avatar (Auth) — the account's own picture
  *   - GET/PATCH /api/users/{id} (Auth) — the Users page's Edit user form
  *   - GET /api/users/{id}/avatar (Auth) — one account's picture (admin/analyst)
+ *   - GET /api/users/tmux, POST /api/users/{id}/tmux-restart, POST /api/users/tmux-restart-idle
+ *     (Auth) — each member's own tmux server and an admin's restart of it (S3)
  * Exports `{ tags, schemas, paths }`, combined into the spec by
  * server/openapi-extra.js. See docs/SERVER-MODE.md.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
@@ -409,6 +411,77 @@ const paths = {
       },
     },
   },
+  "/api/users/tmux": {
+    get: {
+      tags: ["Auth"],
+      operationId: "listMemberTmux",
+      summary:
+        "Each member's own tmux server (one Linux user per account): its version beside the installed one, sessions, agents working (admin/analyst)",
+      responses: {
+        200: {
+          description:
+            "{available, installed, matched, users: [{id, username, running, stuck?, version, pid, startedAt, sessions, busy, outdated}]} — available false without S3",
+        },
+        403: err("EADMIN — a developer"),
+      },
+    },
+  },
+  "/api/users/{id}/tmux-restart": {
+    post: {
+      tags: ["Auth"],
+      operationId: "restartMemberTmux",
+      summary:
+        "End one member's tmux server — every pane of theirs closes; the next start runs the installed tmux (admin, own password again, audited)",
+      parameters: [idParam],
+      requestBody: {
+        required: true,
+        content: {
+          "application/json": {
+            schema: {
+              type: "object",
+              required: ["currentPassword"],
+              properties: { currentPassword: { type: "string" } },
+            },
+          },
+        },
+      },
+      responses: {
+        200: { description: "{user}" },
+        403: err("EREAUTH (own password wrong) / EADMIN / ELOCALMODE"),
+        404: err("ENOUSER"),
+        409: err(
+          "ETMUXSTUCK — the server did not stop (the message names the pid for root) / ENOS3"
+        ),
+      },
+    },
+  },
+  "/api/users/tmux-restart-idle": {
+    post: {
+      tags: ["Auth"],
+      operationId: "restartIdleMemberTmux",
+      summary:
+        "Restart every member server older than the installed tmux while no agent of theirs works (admin, own password again, audited per member)",
+      requestBody: {
+        required: true,
+        content: {
+          "application/json": {
+            schema: {
+              type: "object",
+              required: ["currentPassword"],
+              properties: { currentPassword: { type: "string" } },
+            },
+          },
+        },
+      },
+      responses: {
+        200: {
+          description:
+            "{restarted: [username], skipped: [username — an agent working], failed: [{username, message}]}",
+        },
+        403: err("EREAUTH / EADMIN / ELOCALMODE"),
+      },
+    },
+  },
   "/api/users/{id}/avatar": {
     get: {
       tags: ["Auth"],