feat: v2.8.0 — Artifacts uploads and plugin links, console tab combos, account avatars

- Artifacts hub: upload a file from the computer; make a skill by uploading a
  Markdown file, files, a folder or a .zip/.skill, or by writing it in the
  dialog; add plugins by picking from the list a marketplace link answers
  (POST /api/artifacts/plugin/inspect); Settings → AI tools → Artifacts Hub.
- Console tabs are combos of up to four split panes (ConsoleTabs, PaneGrid).
- Accounts: an own avatar (PUT/DELETE /api/me/avatar, raster only, ≤ 1 MB,
  <data dir>/avatars/), shown with name and role at the sidebar's foot and on
  the workspace owner groups (GET /api/users/:id/avatar, owner_avatar_at).
- Users page: per-user storage (GET /api/users/storage, measured in a worker)
  and account-pool spend/tokens per account (server/lib/pool-usage.js).

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

client/src/components/users/UserAvatar.tsx

@@ -0,0 +1,59 @@
+/**
+ * @file UserAvatar.tsx
+ * @description An account's round picture: the signed-in account's own
+ * (`GET /api/me/avatar`) or, with `userId`, another's (`GET
+ * /api/users/:id/avatar`, staff only), versioned by `avatarAt`; without one —
+ * or when the image fails to load — the first letters of its name. Used by the
+ * sidebar's account row, its workspace owner groups and Settings → Account.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { useState } from "react";
+import { api } from "../../lib/api";
+
+export function UserAvatar({
+  name,
+  avatarAt,
+  userId,
+  letters = 2,
+  className = "h-7 w-7 text-[11px]",
+  initialsClassName = "bg-accent/15 text-accent",
+}: {
+  name: string;
+  avatarAt?: string | null;
+  /** Another account's (staff only); omitted = the signed-in account's own. */
+  userId?: number;
+  /** How many letters of the name stand in for a missing picture. */
+  letters?: number;
+  /** Size and font size: the parts that differ between call sites. */
+  className?: string;
+  /** The initials' colours. */
+  initialsClassName?: string;
+}) {
+  const url = userId != null ? api.users.avatarUrl(userId, avatarAt) : api.me.avatarUrl(avatarAt);
+  // A broken image falls back to the initials, per URL.
+  const [failed, setFailed] = useState<string | null>(null);
+  const base = `flex flex-shrink-0 items-center justify-center overflow-hidden rounded-full ${className}`;
+  if (url && failed !== url) {
+    return (
+      <img
+        src={url}
+        alt=""
+        aria-hidden
+        draggable={false}
+        onError={() => setFailed(url)}
+        className={`${base} object-cover`}
+        data-testid="user-avatar-img"
+      />
+    );
+  }
+  return (
+    <span
+      aria-hidden
+      className={`${base} ${initialsClassName} font-semibold uppercase`}
+      data-testid="user-avatar-initials"
+    >
+      {name.slice(0, letters)}
+    </span>
+  );
+}