chore: v2.8.13 — Artifacts reinstall/edit/installs, agent steps in chat, pick a local file to attach, Windows paths as links

- Chat: an Agent step shows its task, status and tool calls and opens its conversation in place; Windows paths (E:\…, C:/…) in replies open as files
- Prompt: attach a file on this computer by path (native picker), clearer too-large messages
- Artifacts: edit title/description and a skill's files (new snapshot), Reinstall, install history, Hub-only rows, skills installed into ~/.claude/skills and ~/.agents/skills
- Files: batch upload of small files in one extract
- AI Tools: npm install falls back to --prefix ~/.local when the global prefix is not writable

package.json

@@ -1,6 +1,6 @@
 {
   "name": "agenthub",
-  "version": "2.8.12",
+  "version": "2.8.13",
   "bin": {
     "agenthub": "bin/agenthub.js"
   },