feat: right-click menus in Files/Users/Artifacts; several SSH keys and accounts per host

- Files: right-click a sidebar workspace (Open, Copy path) or home (Open,
  Open Trash), a path crumb (Open, Download as zip, Paste into, Copy path),
  a Trash row (Restore, Copy path, Delete forever), the Trash area (Refresh,
  Empty Trash) and an admin's per-user Trash folder (Open, Empty Trash).
- Users: row menu (Edit + Open home in Files for an admin, Copy username/email).
- Artifacts: card menu repeating its buttons, plus Copy link for a page.
- Git identity: named SSH keys beside the default ones (id_<type>_<name>,
  max 10, DELETE ?id=); SSH logins per alias (`ssh://<alias>/` →
  `ssh://<user>@<host>/`, so several AWS CodeCommit accounts share a host),
  each optionally tied to one key (`agenthub.<from>.sshKey`) — a clone of
  that URL offers only that key and persists it. Terminal sshCommand follows
  the keys. Settings → Git: "More SSH keys" + account name/key in the AWS and
  other-host forms. Docs/API.md, OpenAPI updated.

client/src/pages/Artifacts.tsx

@@ -11,7 +11,8 @@
  * admin's switch in Settings → AI tools (`ArtifactsHubSettings`) turns Hub
  * installs off for everyone. Previews of a file are
  * the server's sandboxed `raw` route in a sandboxed iframe, so nothing a
- * shared HTML file carries runs on the dashboard's origin.
+ * shared HTML file carries runs on the dashboard's origin. Right-clicking a
+ * card offers the same actions as its buttons, plus copying a page's link.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -43,6 +44,8 @@ import { eventBus } from "../lib/eventBus";
 import { toast } from "../lib/toast";
 import { confirmDialog } from "../lib/confirm";
 import { useDialog } from "../hooks/useDialog";
+import { copyText } from "../lib/clipboard";
+import { ContextMenu, MenuItem, MenuSeparator, useContextMenu } from "../components/ContextMenu";
 import {
   FileUploadPanel,
   PluginAddPanel,
@@ -325,12 +328,20 @@ function ArtifactCard({
 }) {
   const { t } = useTranslation("artifacts");
   const Icon = KIND_ICON[a.kind];
+  const menu = useContextMenu<null>();
+  const pick = (fn: () => void) => () => {
+    menu.close();
+    fn();
+  };
+  const previewPath = a.kind === "skill" ? "SKILL.md" : (a.files[0]?.path ?? "");
+  const canPreview = (a.kind === "file" || a.kind === "skill") && a.files.length > 0;
   const btn =
     "flex items-center gap-1 rounded px-1.5 py-0.5 text-[11px] text-fg-secondary hover:bg-surface-3 hover:text-fg-primary";
   return (
     <li
       className="flex flex-col gap-2 rounded-lg border border-border bg-surface-1 p-3"
       data-testid={`artifact-${a.id}`}
+      onContextMenu={(e) => menu.open(e, null)}
     >
       <div className="flex items-start gap-2">
         <Icon className="mt-0.5 h-4 w-4 shrink-0 text-fg-muted" />
@@ -363,12 +374,8 @@ function ArtifactCard({
             {t("open")}
           </a>
         )}
-        {(a.kind === "file" || a.kind === "skill") && a.files.length > 0 && (
-          <button
-            type="button"
-            className={btn}
-            onClick={() => onPreview(a.kind === "skill" ? "SKILL.md" : (a.files[0]?.path ?? ""))}
-          >
+        {canPreview && (
+          <button type="button" className={btn} onClick={() => onPreview(previewPath)}>
             <Eye className="h-3 w-3" />
             {t("preview")}
           </button>
@@ -410,6 +417,47 @@ function ArtifactCard({
           )}
         </span>
       </div>
+      {menu.menu && (
+        <ContextMenu x={menu.menu.x} y={menu.menu.y} onClose={menu.close} testId="artifact-menu">
+          {a.kind === "page" && a.url && (
+            <>
+              <MenuItem onSelect={pick(() => window.open(a.url!, "_blank", "noopener,noreferrer"))}>
+                {t("open")}
+              </MenuItem>
+              <MenuItem onSelect={pick(() => void copyText(a.url!))}>{t("copyLink")}</MenuItem>
+            </>
+          )}
+          {canPreview && (
+            <MenuItem onSelect={pick(() => onPreview(previewPath))}>{t("preview")}</MenuItem>
+          )}
+          {a.kind === "file" && a.files.length > 0 && (
+            <MenuItem
+              onSelect={pick(() => {
+                window.location.href = api.artifacts.rawUrl(a.id, a.files[0]?.path, true);
+              })}
+            >
+              {t("download")}
+            </MenuItem>
+          )}
+          {(a.kind === "skill" || a.kind === "plugin") && (
+            <MenuItem disabled={!canInstall} onSelect={pick(onInstall)}>
+              {t("install")}
+            </MenuItem>
+          )}
+          {a.canChange && (
+            <>
+              <MenuSeparator />
+              {server && (
+                <MenuItem onSelect={pick(onShare)}>{t(a.shared ? "unshare" : "share")}</MenuItem>
+              )}
+              <MenuItem onSelect={pick(onRename)}>{t("rename")}</MenuItem>
+              <MenuItem danger onSelect={pick(onDelete)}>
+                {t("delete")}
+              </MenuItem>
+            </>
+          )}
+        </ContextMenu>
+      )}
     </li>
   );
 }