feat(server-s3): one Linux user per account (S3) — experimental

Server mode can now run each account as its own Linux user (ah-<name>)
when `agenthub server install-system` has set S3 up. The dashboard
reaches a member only through sudo -u / write-as / pane-launch, reads a
member's files only through owner- and type-checked opens, and hooks
are authenticated by peer uid. Local mode and server mode without S3
are unchanged.

EXPERIMENTAL: tested with fake sudo and fake accounts only. It has not
yet been verified on a real install with real member accounts, sudo or
a real Codex login. Do not offer it to real users yet.

- S3 core: provisioning, per-member tmux servers, the proxy key
  gateway, shared tools in /opt, dropped capabilities for children
  (P0–P5)
- P4: plan and quota per member home
- P6: ~/.claude.json seed; opt-in plugin baseline installed as the
  member; managed-settings spike script (not run)
- P7: Codex account pool (`agenthub accounts add --tool codex`)
- Roles merged with main's admin / analyst / developer: analysts write
  only their own rows, under S3 as well
- Per-account prefs: one implementation (Chat UI + onboarding)
- Security reviews F1–F49 (five rounds), each fix with a regression
  test: symlink/TOCTOU-safe member reads, no host writes in a member
  home, credentials and the data dir never served, owner and folder
  account must agree, pane tokens bound to the pane's uid, bounded
  sudo/tmux/git calls and member reads (no hang or crash from a member),
  async route rejections answer 500 instead of exiting
- Docs: docs/SERVER-MODE.md (S3 model, accepted ceilings, operator
  runbook), docs/plans/server-mode/S3-PLAN.md, CLAUDE.md S3 rules

Tests: server 2838/2841 (3 need 127.0.0.1:3000, held on this box);
client 1162/1162; tsc clean; headers check passes.

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

server/openapi-extra/auth.js

@@ -3,9 +3,10 @@
  *   - GET  /api/auth/me      (Auth)
  *   - POST /api/auth/login   (Auth)
  *   - POST /api/auth/logout  (Auth)
- *   - GET  /api/accounts     (Auth) — the Claude account pool, no tokens
+ *   - GET  /api/accounts     (Auth) — the Claude and Codex account pools, no keys or tokens
  *   - GET  /api/users        (Auth) — every account's usage (admin/analyst)
  *   - GET  /api/users/audit  (Auth) — staff reads of developers' sessions
+ *   - GET/PUT /api/me/prefs, POST /api/me/onboarded (Auth) — the account's own UI preferences
  * 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>
@@ -20,6 +21,14 @@ const tags = [
 ];
 
 const schemas = {
+  UserPrefs: {
+    type: "object",
+    required: ["prefs", "onboardedAt"],
+    properties: {
+      prefs: { type: "object", additionalProperties: { type: "string" } },
+      onboardedAt: { type: "string", nullable: true },
+    },
+  },
   AuthUser: {
     type: "object",
     required: ["id", "username", "role"],
@@ -72,13 +81,59 @@ const changeBody = (properties, required = []) => ({
 const changeResponses = {
   200: { description: "Changed", content: userBody },
   400: err("EBADPASSWORD / EBADROLE / EBADFIELD"),
-  403: err("EREAUTH (own password wrong) / EREADONLY / EADMIN / ELOCALMODE"),
+  403: err("EREAUTH (own password wrong) / EADMIN / ELOCALMODE"),
   404: err("ENOUSER / ENOLANE"),
   409: err("ESELF — your own role or disable"),
   429: err("ETOOMANY — 10 wrong passwords in 15 minutes"),
 };
 
+const prefsBody = {
+  "application/json": { schema: { $ref: "#/components/schemas/UserPrefs" } },
+};
+
 const paths = {
+  "/api/me/prefs": {
+    get: {
+      tags: ["Auth"],
+      summary: "The signed-in account's own UI preferences",
+      description:
+        "Local mode is the one account `local`; server mode one row per account. Keys are the browser's localStorage names (docs/API.md).",
+      responses: { 200: { description: "Preferences", content: prefsBody }, 401: err("EAUTH") },
+    },
+    put: {
+      tags: ["Auth"],
+      summary: "Merge the account's preferences (null deletes a key)",
+      requestBody: {
+        required: true,
+        content: {
+          "application/json": {
+            schema: {
+              type: "object",
+              required: ["prefs"],
+              properties: {
+                prefs: {
+                  type: "object",
+                  additionalProperties: { type: "string", nullable: true, maxLength: 8192 },
+                },
+              },
+            },
+          },
+        },
+      },
+      responses: {
+        200: { description: "Saved", content: prefsBody },
+        400: err("EBADPREFS — an unknown key or a value that is not a short string"),
+        401: err("EAUTH"),
+      },
+    },
+  },
+  "/api/me/onboarded": {
+    post: {
+      tags: ["Auth"],
+      summary: "The account went through (or skipped) the first-run setup",
+      responses: { 200: { description: "Marked", content: prefsBody }, 401: err("EAUTH") },
+    },
+  },
   "/api/users": {
     get: {
       tags: ["Auth"],
@@ -153,7 +208,7 @@ const paths = {
       responses: {
         201: { description: "Created", content: userBody },
         400: err("EBADUSER / EBADPASSWORD / EBADROLE"),
-        403: err("EREAUTH (own password wrong) / EREADONLY / EADMIN / ELOCALMODE"),
+        403: err("EREAUTH (own password wrong) / EADMIN / ELOCALMODE"),
         409: err("EEXISTS"),
         429: err("ETOOMANY — 10 wrong passwords in 15 minutes"),
       },
@@ -235,7 +290,8 @@ const paths = {
     get: {
       tags: ["Auth"],
       operationId: "listPoolAccounts",
-      summary: "The Claude account pool as the balancer sees it (never a token)",
+      summary:
+        "The Claude and Codex account pools as the balancer sees them (never a key or token)",
       parameters: [
         {
           name: "force",
@@ -271,6 +327,25 @@ const paths = {
                       },
                     },
                   },
+                  codex: {
+                    type: "array",
+                    description:
+                      "The Codex account pool (server/lib/codex-pool.js), same fields plus `kind`; no expiry",
+                    items: {
+                      type: "object",
+                      properties: {
+                        name: { type: "string" },
+                        kind: { type: "string", enum: ["apikey", "chatgpt"] },
+                        addedAt: { type: "string" },
+                        livePanes: { type: "integer" },
+                        spend5h: { type: "number" },
+                        spend7d: { type: "number" },
+                        quota: { type: "object", nullable: true },
+                        quotaPercent: { type: "number", nullable: true },
+                        full: { type: "boolean" },
+                      },
+                    },
+                  },
                 },
               },
             },