feat(artifacts): capture Claude Docs docs and session documents, claim unowned rows

- A Claude Docs `batch` that creates a doc is captured like an `Artifact`
  publish, titled by the doc's name and linked by its own frame URL.
- At Stop/SessionEnd, each pptx/docx/xlsx/pdf/html a workspace session
  created or changed is snapshotted into its owner's library (`auto`);
  an unchanged file is skipped, a changed one refreshes its snapshot.
- Server mode: a page with no owner carries a suggested owner (the
  workspace or home its session ran in). The suggested user claims or
  declines it; an admin claims or assigns any. New tab Unowned /
  Is this yours? on the Artifacts page; all three actions audited.

client/src/pages/Artifacts.tsx

@@ -49,7 +49,9 @@ import {
   type ArtifactInstalls,
   type ArtifactKind,
   type ArtifactSettings,
+  type ServerUserUsage,
 } from "../lib/api";
+import { usePermissions } from "../components/AuthGate";
 import type { Lane } from "../lib/types";
 import { eventBus } from "../lib/eventBus";
 import { toast } from "../lib/toast";
@@ -114,7 +116,11 @@ const footAction =
 export function Artifacts() {
   const { t } = useTranslation("artifacts");
   const [settings, setSettings] = useState<ArtifactSettings | null>(null);
-  const [tab, setTab] = useState<"all" | "mine" | "hub">("all");
+  const [tab, setTab] = useState<"all" | "mine" | "hub" | "unowned">("all");
+  const { isAdmin } = usePermissions();
+  // Server mode: rows nobody owns — every one for an admin, those offered to you otherwise.
+  const [unownedCount, setUnownedCount] = useState(0);
+  const [users, setUsers] = useState<ServerUserUsage[]>([]);
   const [kind, setKind] = useState<ArtifactKind | "">("");
   const [q, setQ] = useState("");
   const [items, setItems] = useState<Artifact[] | null>(null);
@@ -147,14 +153,45 @@ export function Artifacts() {
     return () => window.clearTimeout(id);
   }, [load, q]);
 
+  const serverMode = !!settings?.serverMode;
+  const countUnowned = useCallback(() => {
+    if (!serverMode) return;
+    api.artifacts
+      .list({ scope: "unowned" })
+      .then((r) => setUnownedCount(r.items.length))
+      .catch(() => setUnownedCount(0));
+  }, [serverMode]);
+  useEffect(countUnowned, [countUnowned]);
+  useEffect(() => {
+    if (tab !== "unowned" || !isAdmin || users.length) return;
+    api.users
+      .list()
+      .then((r) => setUsers(r.users.filter((u) => !u.disabled)))
+      .catch(() => setUsers([]));
+  }, [tab, isAdmin, users.length]);
+
   useEffect(
     () =>
       eventBus.subscribe((msg) => {
-        if (msg.type === "artifact_changed") load();
+        if (msg.type === "artifact_changed") {
+          load();
+          countUnowned();
+        }
       }),
-    [load]
+    [load, countUnowned]
   );
 
+  const settle = async (run: () => Promise<unknown>, done: string) => {
+    try {
+      await run();
+      toast.success(t(done));
+      load();
+      countUnowned();
+    } catch (err) {
+      toast.error(err);
+    }
+  };
+
   // The Add menu closes on Escape or a click anywhere outside it.
   useEffect(() => {
     if (!addMenu) return;
@@ -297,15 +334,63 @@ export function Artifacts() {
     },
   });
 
-  const card = (a: Artifact) => (
-    <ArtifactCard
-      key={a.id}
-      item={a}
-      server={server}
-      canInstall={!!settings?.installsEnabled}
-      {...actionsFor(a)}
-    />
-  );
+  const card = (a: Artifact) =>
+    tab === "unowned" ? (
+      <div key={a.id} className="flex flex-col gap-2" data-testid={`unowned-${a.id}`}>
+        <ArtifactCard
+          item={a}
+          server={server}
+          canInstall={!!settings?.installsEnabled}
+          {...actionsFor(a)}
+        />
+        <div className="flex flex-wrap items-center gap-2 text-xs">
+          {(a.suggestedForMe || isAdmin) && (
+            <button
+              type="button"
+              className="btn-primary px-2 py-1 text-xs"
+              onClick={() => settle(() => api.artifacts.claim(a.id), "unowned.claimed")}
+            >
+              {t(a.suggestedForMe ? "unowned.mine" : "unowned.takeIt")}
+            </button>
+          )}
+          {a.suggestedForMe && (
+            <button
+              type="button"
+              className={footAction}
+              onClick={() => settle(() => api.artifacts.decline(a.id), "unowned.declined")}
+            >
+              {t("unowned.notMine")}
+            </button>
+          )}
+          {isAdmin && users.length > 0 && (
+            <select
+              className="input h-7 w-auto py-0 text-xs"
+              aria-label={t("unowned.assign")}
+              value=""
+              onChange={(e) => {
+                const userId = Number(e.target.value);
+                if (userId) settle(() => api.artifacts.assign(a.id, userId), "unowned.assigned");
+              }}
+            >
+              <option value="">{t("unowned.assign")}</option>
+              {users.map((u) => (
+                <option key={u.id} value={u.id}>
+                  {u.displayName || u.username}
+                </option>
+              ))}
+            </select>
+          )}
+        </div>
+      </div>
+    ) : (
+      <ArtifactCard
+        key={a.id}
+        item={a}
+        server={server}
+        canInstall={!!settings?.installsEnabled}
+        {...actionsFor(a)}
+      />
+    );
 
   // Local mode (everything is yours): the unfiltered page is shelved by
   // kind; a category or a search is one flat grid of results.
@@ -320,7 +405,7 @@ export function Artifacts() {
   // what you shared, My library into what you installed from others (the
   // server adds those to `mine`) and your own.
   const halves =
-    server && items
+    server && items && tab !== "unowned"
       ? (["others", "own"] as const).map((who) => ({
           key: `${tab}.${who}`,
           rows: items.filter((a) => (who === "own" ? a.mine : !a.mine)),
@@ -424,12 +509,29 @@ export function Artifacts() {
                 {t(`tab.${v}`)}
               </button>
             ))}
+            {(isAdmin || unownedCount > 0 || tab === "unowned") && (
+              <button
+                type="button"
+                aria-pressed={tab === "unowned"}
+                onClick={() => setTab("unowned")}
+                className={segment(tab === "unowned")}
+                data-testid="artifacts-tab-unowned"
+                title={t(isAdmin ? "unowned.hintAdmin" : "unowned.hint")}
+              >
+                {t(isAdmin ? "tab.unowned" : "tab.suggested")}
+                {unownedCount > 0 && <span className="ml-1 text-fg-muted">{unownedCount}</span>}
+              </button>
+            )}
           </div>
         )}
       </div>
 
       {items === null ? (
         <SkeletonGrid label={t("loading")} />
+      ) : items.length === 0 && tab === "unowned" ? (
+        <p className="rounded-lg border border-dashed border-border px-4 py-6 text-center text-xs text-fg-muted">
+          {t("unowned.empty")}
+        </p>
       ) : items.length === 0 ? (
         <EmptyState
           hub={tab === "hub"}
@@ -755,6 +857,11 @@ function ArtifactCard({
           {t(hubOnly ? "hubOnly" : "shared")}
         </span>
       )}
+      {a.auto && (
+        <span className="badge self-start" title={t("autoHint")}>
+          {t("auto")}
+        </span>
+      )}
       {a.description && (
         <p className="line-clamp-2 text-xs leading-relaxed text-fg-secondary">{a.description}</p>
       )}