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.

server/routes/git-identity.js

@@ -1,10 +1,12 @@
 /**
  * @file HTTP surface for a user's OWN git identity (`server/lib/git-identity.js`),
- * mounted at `/api/me/git`: the SSH keys a clone uses — ed25519 and/or rsa (make, replace, delete —
- * only the PUBLIC key is ever returned) and the HTTPS logins (save, delete —
- * `hasToken` only, never a password), whether the account's own terminal
- * git uses that key (`core.sshCommand`), the SSH login name per host
- * (`url.<…>.insteadOf` — AWS CodeCommit's SSH key ID), and the commit author (`user.name` /
+ * mounted at `/api/me/git`: the SSH keys a clone uses — a default ed25519
+ * and/or rsa one plus named ones (`name`, deleted by `?id=`) for more
+ * accounts (make, replace, delete — only the PUBLIC key is ever returned) and
+ * the HTTPS logins (save, delete — `hasToken` only, never a password),
+ * whether the account's own terminal git uses the keys (`core.sshCommand`),
+ * the SSH logins per host or alias (`url.<…>.insteadOf` — AWS CodeCommit's
+ * SSH key ID — each optionally tied to one key), and the commit author (`user.name` /
  * `user.email` of the account's global git config — a member's commits fail
  * without one; a new SSH key is labelled with that email, else
  * `<username>@smartgift.vn`). The account is the signed-in user's
@@ -33,6 +35,10 @@ const STATUS = {
   EBADKEYTYPE: 400,
   EFOREIGNSSH: 409,
   EBADSSHUSER: 400,
+  EBADKEYNAME: 400,
+  ETOOMANYKEYS: 409,
+  EBADALIAS: 400,
+  ENOKEY: 400,
 };
 
 function fail(res, e) {
@@ -87,9 +93,10 @@ router.post("/ssh-key", sameOriginGuard, async (req, res) => {
     await identity.generateSshKey(account, {
       replace: req.body?.replace === true,
       type: req.body?.type === "rsa" ? "rsa" : "ed25519",
+      // A named key sits beside the default one of its type.
+      name: typeof req.body?.name === "string" ? req.body.name : null,
       // The key is labelled with the commit author's email, else the default one.
-      comment:
-        (await identity.getAuthor(account)).email || identity.defaultEmail(usernameOf(req)),
+      comment: (await identity.getAuthor(account)).email || identity.defaultEmail(usernameOf(req)),
     });
     res.status(201).json(await view(account, usernameOf(req)));
   } catch (e) {
@@ -101,7 +108,8 @@ router.delete("/ssh-key", sameOriginGuard, async (req, res) => {
   try {
     const account = accountOf(req, { write: true });
     const type = req.query.type === undefined ? undefined : String(req.query.type);
-    if (!(await identity.removeSshKey(account, type))) {
+    const id = req.query.id === undefined ? undefined : String(req.query.id);
+    if (!(await identity.removeSshKey(account, { type, id }))) {
       return res.status(404).json({ error: { code: "ENOTFOUND", message: "no SSH key" } });
     }
     res.json(await view(account, usernameOf(req)));
@@ -128,8 +136,10 @@ router.put("/ssh-terminal", sameOriginGuard, async (req, res) => {
 });
 
 /**
- * The SSH user name for one host (`{host, user}`) — e.g. AWS CodeCommit's SSH
- * key ID, so a plain `ssh://git-codecommit…/` URL logs in. DELETE drops it.
+ * An SSH login (`{host, user, alias?, key?}`) — e.g. AWS CodeCommit's SSH key
+ * ID, so a plain `ssh://git-codecommit…/` URL logs in; with `alias`, one more
+ * account on that host (`ssh://<alias>/…`); with `key`, the only key it uses.
+ * DELETE `/ssh-user/<host or alias>` drops it.
  */
 router.put("/ssh-user", sameOriginGuard, async (req, res) => {
   try {