chore: v2.8.21 — update progress steps, clone in background, extra SSH keys inline, today's spend

- Plugin update reports its running step (plugin-update-progress.json →
  plugin_update_progress); a hidden update or clone leaves a progress chip.
- Clone here can run in the background.
- Git identity: extra SSH keys are added inline per host (no More keys tab).
- Users: spend today (viewer's local day, ?tz_offset=).
- Prettier on the files touched since v2.8.20.

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "agenthub",
-  "version": "2.8.20",
+  "version": "2.8.21",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "agenthub",
-      "version": "2.8.20",
+      "version": "2.8.21",
       "hasInstallScript": true,
       "license": "UNLICENSED",
       "dependencies": {