feat(artifacts): last updated time on skills and files; each installer's copy marked

A row said nothing about when its content last changed, and the install list
could not tell who still runs an old version. `artifacts.version_at` (new
column, existing rows from `updated_at`) is stamped only when a snapshot is
replaced — a rename or share toggle leaves it — and served as `versionAt`:
skill and file rows read "Updated 3h ago", the detail sheet "Last updated".
`GET /api/artifacts/:id/installs` gives each skill install a `state` —
latest / outdated / removed / unknown — from its Claude skill copies' hash
against the newest snapshot, shown as a badge.

client/src/i18n/locales/en/artifacts.json

@@ -142,6 +142,11 @@
   "installsYou": "You",
   "installsUnknown": "A removed user",
   "installsReplaced": "replaced an older copy",
+  "versionAt": "Updated {{ago}}",
+  "versionAtFull": "Last updated {{date}}",
+  "installState.latest": "Latest",
+  "installState.outdated": "Old version",
+  "installState.removed": "Removed",
   "installsPluginWhere": "claude plugin install --scope user",
   "installsUnrecorded": "{{count}} earlier installs were counted before details were kept",
   "installsNoneOfYours": "You have not installed it — only your own installs are listed.",
@@ -185,7 +190,7 @@
   "stat.installs": "Installs",
   "stat.files": "Files",
   "stat.size": "Size",
-  "stat.updated": "Updated",
+  "stat.updated": "Last updated",
   "detail.runAs": "Run it as",
   "detail.market": "Marketplace",
   "detail.added": "Added {{date}}",

client/src/i18n/locales/vi/artifacts.json

@@ -143,6 +143,11 @@
   "installsYou": "Bạn",
   "installsUnknown": "Người dùng đã xoá",
   "installsReplaced": "thay bản cũ",
+  "versionAt": "Cập nhật {{ago}}",
+  "versionAtFull": "Cập nhật lần cuối {{date}}",
+  "installState.latest": "Bản mới nhất",
+  "installState.outdated": "Bản cũ",
+  "installState.removed": "Đã gỡ",
   "installsPluginWhere": "claude plugin install --scope user",
   "installsUnrecorded": "{{count}} lượt cài trước đây chỉ được đếm, không lưu chi tiết",
   "installsNoneOfYours": "Bạn chưa cài — chỉ hiện các lượt cài của bạn.",
@@ -186,7 +191,7 @@
   "stat.installs": "Lượt cài",
   "stat.files": "File",
   "stat.size": "Dung lượng",
-  "stat.updated": "Cập nhật",
+  "stat.updated": "Cập nhật lần cuối",
   "detail.runAs": "Gọi bằng",
   "detail.market": "Marketplace",
   "detail.added": "Thêm lúc {{date}}",

client/src/lib/api.ts

@@ -4720,11 +4720,21 @@ export interface Artifact {
   suggestedForMe?: boolean;
   createdAt: string;
   updatedAt: string;
+  /** When its content last changed (a new snapshot); a page or plugin: when it was added. */
+  versionAt: string;
 }
 
 /** GET /api/artifacts/:id/installs. `paths` only for your own installs (or an admin). */
 export interface ArtifactInstalls {
-  items: { user: string | null; mine: boolean; at: string; replaced: boolean; paths?: string[] }[];
+  items: {
+    user: string | null;
+    mine: boolean;
+    at: string;
+    replaced: boolean;
+    /** Skills: where that install's copy stands against the newest version now. */
+    state?: "latest" | "outdated" | "removed" | "unknown";
+    paths?: string[];
+  }[];
   /** Installs counted before the list was kept. */
   unrecorded: number;
 }

client/src/pages/Artifacts.tsx

@@ -32,7 +32,10 @@
  * takes its folder on the server — or a plugin's copy — on a click, else
  * asks for the folder and uploads it onto the same row); an installed copy
  * that differs from the newest version shows **Update** (a pack: "Update N"),
- * which replaces it after a confirmation, the old copy moved aside. Editing a skill
+ * which replaces it after a confirmation, the old copy moved aside. A skill or
+ * file row says when its CONTENT last changed ("Updated 3h ago", `versionAt`),
+ * and the install count's list marks each installer's copy Latest / Old
+ * version / Removed. Editing a skill
  * edits its SKILL.md (name, description, instructions — a new snapshot);
  * its preview opens with what it installs as and when Claude uses it. Deleting a shared
  * row of your own only takes it out of your library — it stays in the Hub
@@ -81,6 +84,7 @@ import { toast } from "../lib/toast";
 import { confirmDialog } from "../lib/confirm";
 import { useDialog } from "../hooks/useDialog";
 import { copyText } from "../lib/clipboard";
+import { timeAgo } from "../lib/format";
 import { ContextMenu, MenuItem, MenuSeparator, useContextMenu } from "../components/ContextMenu";
 import {
   FileUploadPanel,
@@ -1271,6 +1275,7 @@ function Meta({
   server: boolean;
   date?: boolean;
 }) {
+  const { t } = useTranslation("artifacts");
   const parts: React.ReactNode[] = [];
   if (server && a.owner && !a.mine)
     parts.push(
@@ -1278,7 +1283,18 @@ function Meta({
         {a.owner}
       </span>
     );
-  if (date)
+  // A skill or file is a snapshot that changes: when it last did. Anything else: when added.
+  if (a.kind === "skill" || a.kind === "file")
+    parts.push(
+      <span
+        key="at"
+        className="shrink-0"
+        title={t("versionAtFull", { date: new Date(a.versionAt).toLocaleString() })}
+      >
+        {t("versionAt", { ago: timeAgo(a.versionAt) })}
+      </span>
+    );
+  else if (date)
     parts.push(
       <span key="at" className="shrink-0" title={new Date(a.createdAt).toLocaleString()}>
         {fmtDate(a.createdAt)}
@@ -1536,7 +1552,10 @@ function DetailDialog({
       : []),
     ...(a.files.length ? [{ label: t("stat.files"), value: String(a.files.length) }] : []),
     ...(a.size ? [{ label: t("stat.size"), value: fmtBytes(a.size) }] : []),
-    { label: t("stat.updated"), value: fmtDate(a.updatedAt) },
+    {
+      label: t("stat.updated"),
+      value: new Date(a.versionAt).toLocaleString(),
+    },
   ];
   return (
     <Modal title={a.title} onClose={onClose} size="md">
@@ -1707,6 +1726,13 @@ function DetailDialog({
  *  The list floats over the page (a portal at the button, below it or above
  *  when there is no room, kept inside the window): inside the card list's
  *  `overflow-hidden` it was cut off at the last card. */
+/** An installer's copy against the newest version: green, amber, grey. */
+const STATE_CLASS = {
+  latest: "bg-status-success/15 text-status-success",
+  outdated: "bg-status-warning/15 text-status-warning",
+  removed: "bg-surface-2 text-fg-muted",
+} as const;
+
 function InstallsButton({ item }: { item: Artifact }) {
   const { t } = useTranslation("artifacts");
   const [open, setOpen] = useState(false);
@@ -1798,6 +1824,14 @@ function InstallsButton({ item }: { item: Artifact }) {
                           <span className="ml-1 text-fg-muted">· {t("installsReplaced")}</span>
                         )}
                       </span>
+                      {i.state && i.state !== "unknown" && (
+                        <span
+                          data-testid="install-state"
+                          className={`shrink-0 rounded px-1 text-[10px] ${STATE_CLASS[i.state]}`}
+                        >
+                          {t(`installState.${i.state}`)}
+                        </span>
+                      )}
                       <span className="shrink-0 text-[11px] text-fg-muted">
                         {new Date(i.at).toLocaleString()}
                       </span>

client/src/pages/__tests__/Artifacts.test.tsx

@@ -77,6 +77,7 @@ const item = (over: Partial<Artifact>): Artifact => ({
   installs: 0,
   createdAt: "2026-10-14T00:00:00Z",
   updatedAt: "2026-10-14T00:00:00Z",
+  versionAt: "2026-10-14T00:00:00Z",
   ...over,
 });
 
@@ -349,9 +350,16 @@ describe("Artifacts", () => {
           mine: true,
           at: "2026-10-19T10:00:00Z",
           replaced: false,
+          state: "latest",
           paths: ["/h/.claude/skills/deploy"],
         },
-        { user: "khoa", mine: false, at: "2026-10-18T10:00:00Z", replaced: true },
+        {
+          user: "khoa",
+          mine: false,
+          at: "2026-10-18T10:00:00Z",
+          replaced: true,
+          state: "outdated",
+        },
       ],
       unrecorded: 1,
     });
@@ -363,6 +371,12 @@ describe("Artifacts", () => {
     expect(await within(box).findByText("/h/.claude/skills/deploy")).toBeInTheDocument();
     expect(within(box).getByText(/khoa/)).toBeInTheDocument();
     expect(within(box).getByText(/1 earlier installs/)).toBeInTheDocument();
+    // Each install says whether its copy is the newest version.
+    expect(
+      within(box)
+        .getAllByTestId("install-state")
+        .map((b) => b.textContent)
+    ).toEqual(["Latest", "Old version"]);
     // Over the page, outside the card list that clips its overflow — and a
     // click inside it keeps it open.
     expect(box.parentElement).toBe(document.body);
@@ -436,6 +450,24 @@ describe("Artifacts", () => {
     );
   });
 
+  it("says when a skill's content last changed, not when it was renamed", async () => {
+    vi.mocked(api.artifacts.list).mockResolvedValue({
+      items: [
+        item({
+          id: 2,
+          kind: "skill",
+          title: "deploy",
+          source: "deploy",
+          updatedAt: new Date().toISOString(),
+          versionAt: new Date(Date.now() - 3 * 3600_000).toISOString(),
+        }),
+      ],
+    });
+    open();
+    const card = await screen.findByTestId("artifact-2");
+    expect(within(card).getByText("Updated 3h ago")).toBeInTheDocument();
+  });
+
   it("offers Update for an installed skill its owner changed, after a confirmation", async () => {
     vi.mocked(api.artifacts.list).mockResolvedValue({
       items: [