feat: v2.7.8 — Artifacts hub, clone related repos as extra folders, quieter resume prompt

- Artifacts (/artifacts): claude.ai pages sessions publish (captured from the
  Artifact tool's hook), pinned workspace files, skills and plugins, each
  kept as a snapshot; shared ones appear in a Hub and a skill or plugin
  installs into the viewer's own account (server/lib/artifacts.js,
  /api/artifacts, docs/plans/artifacts/).
- Workspace extra folders: clone one or more related repos beside the
  workspace and add them in one step (POST /api/lanes/:id/sources/clone).
- A pane that ended by itself while tmux kept running is no longer offered
  for resume (tmux.serverStartedAt in reconcileOrphans).
- Changes panel: a folder that is not a git repo opens on Files, and its
  files open from there.
- Plus the parallel sessions' work in this tree: File Explorer button in the
  panel header, user delete, RSA SSH keys, chat/terminal and pet fixes.

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

server/lib/linux-accounts.js

@@ -23,7 +23,7 @@ const { execFileSync } = require("node:child_process");
 /** Lower case, a letter first, ≤ 29 so `ah-<name>` fits Linux's 32. */
 const LINUX_NAME_RE = /^[a-z][a-z0-9_-]{0,28}$/;
 const PROVISION = "/opt/agenthub/sbin/agenthub-provision";
-const ACTIONS = new Set(["create", "disable", "enable"]);
+const ACTIONS = new Set(["create", "disable", "enable", "delete"]);
 
 const confPath = () => process.env.AGENTHUB_SERVER_CONF || "/etc/agenthub/server.conf";
 
@@ -121,7 +121,8 @@ function __setRunImpl(fn) {
 }
 
 /**
- * Create / disable / enable the Linux account of `username`. A no-op outside
+ * Create / disable / enable / delete (account AND home) the Linux account of
+ * `username`. A no-op outside
  * S3 (returns null). Throws EPROVISION with the helper's own words on failure.
  */
 function provision(action, username) {
@@ -135,7 +136,12 @@ function provision(action, username) {
       .trim()
       .split("\n")
       .pop();
-    throw Object.assign(new Error(`could not ${action} the Linux account: ${why}`), {
+    // An installed helper older than this build (root's copy is refreshed
+    // only by install-system) does not know the action yet.
+    const hint = /unknown action/.test(why)
+      ? " — the server helper is older than this AgentHub: run `sudo agenthub server install-system` once"
+      : "";
+    throw Object.assign(new Error(`could not ${action} the Linux account: ${why}${hint}`), {
       code: "EPROVISION",
     });
   }